Your ability of receive all the Freeview transmissions depends on the suitability of aerial
the design style,
the "group", and
its physical location.
Standard type - Yagi aerial
The standard type of TV aerial is known as the Yagi aerial. It is mounted on a pole, and consists of a rod with a reflector (shown green) at the back and many spiky elements (in grey) at the front. The connecting cable connects to the element nearest the reflector, known as the driver (shown in blue).
These Yagi aerials are directional and so pick up signals best from a transmitter that the rod points towards. The more elements the aerial has, the better it picks up a signal and becomes more directional.
A standard-type aerial is all that is required for digital TV reception in most places. These antennae have between 10 and 18 elements and a single reflector. These are recommended for new installations for good digital television reception, but will more often than not function perfectly in good reception areas.
Typically these aerials are designed to receive only some transmission frequencies - see "groups" below.
High Gain aerials
These aerials are designed for poor digitalreception areas, and have two reflectors. For maximum signal strength, some digital high gain aerials have up to 100 elements. Since the switchover to digital-only transmissions back in October 2012, most UK households now have good quality digital TV signals.
A more expensive aerial is only required where the signal strength is low, but can often provide the whole Freeviewreception where it might otherwise be impossible.
The CAI (that represents aerial installers) has four standards for digital TV aerials. The highest standard "1" is for homes on the fringes of coverage areas, intermediate standard "2" is suitable for use within the coverage area; minimum standard "3" is for good coverage conditions.
These aerials can be either wideband, or receive only selected frequencies - see "groups" below.
You may haved used a 'Grid aerial' for analoguereception, but as they are generally unsuitable for Freeview reception, they have now generally been replaced by the Yagi type. However in some places a Grid aerial installation may work for Freeview: otherwise replace with a standard Yagi aerial.
Indoor aerials are generally not suitable for Freeviewreception. In areas of good signal strength it is often possible to receive some transmissions. Even where an aerial works, people often find that may get interruptions to their viewing (or recording).
The best position for a TV aerial is mounted outdoors, as high from the ground as possible, pointing directly at the transmitter. The signal can be blocked by hills and tall buildings. It should be positioned away from any other aerials.
Horizontal or vertical?
The transmitter will either use vertical mode which requires the elements of your aerial to be up-down, or horizontal mode which requires them to be level with the ground.
Both analogue and digital television is transmitted the same group of transmission frequencies (known as channel 21 through to 60). A coloured marking on the aerial shows the group.
To create the best possible analoguepicture, TV transmissions from adjacent transmitters have been designated to several different groups of frequencies. By using an aerial that receives only the channels in the correct group, the analogue picture can be kept free from interference.
To receive Freeview transmissions from the same transmitter it has been sometimes necessary to use frequencies that are not part of the transmitter's normal group. When this has occurred, the aerial will need to be replaced with a "wideband" aerial (also known as group W) - one that covers every group.
As Ofcom is planning to move the TV frequencies again - perhaps as soon as 2018 - it may be wise to use a widebandaerial if you can to ensure you can keep viewing Freeview for many years to come.
It is because they are far more suitable for current and future reception from all transmitters. A 'grouped' Yagi aerial is only suitable for a part of the UHF band used for TV broadcasting. For example, a Group C/D aerial is only of use for channels 49 and above but is not very good below that and it gets worse the lower the channel numbers. Nowadays, most main transmitters not only have the SD multiplexes but also some HD ones which are often (but not always) in the 31-37 range and a Group C/D Yagi aerial would not be much use. A 'wide band' Yagi is not that good either as its reception ability is quite variable across the bands used for TV so some signals will be noticably stronger than others and maybe the ones you want are the weakest - giving rise to reception problems often reported by the set as 'No Signal'.
One of the benefits of a log-periodic are that they have a fairly flat reception characteristic across the whole UHF band from channel 21 to at least channel 60. That means it can be used for reception of all the signals being broadcast currently. The future plans of Ofcom include the idea of putting all terrestrialdigital TV (Freeview) into the lower channels range so by fitting a log-periodic you would be able to receive your current programmes as well as being as 'future proof' as is possible - unless the Ofcom plans change in the meantime. Log-periodic aerials are no more nor less susceptible to use by our 'feathered friends' as a roost than any other aerial.
The area you mention is not unusual as these better aerials are appearing all over the country, I had one installed in Wiltshire recently so that our new TV would be able to get all the SD and HD channels now and into the foreseeable future. I chose one because I know they are better having been in the TV industry since 1960.
If you are considering having your aerial changed, I would strongly advise having a log-periodic fitted and ignore any advice about needing a 'digital' aerial as there is no such thing.