If you have a brand new aerial, then I would have thought your aerial installer would have aligned it for the best signal strength which in your case would have been the Wenvoe ? transmitter. You could always ask him to come back and realign the aerial to your local transmitter (like your neighbours) but possibly you are shielded by hills, buildings etc. from getting a good signal. You may require a larger aerial with an amplifier, you will definitely need a different group aerial. Wenvoe is group B, whilst Mendips is group C/D. Good luck.