The thing with Freeview is, when it is good it is good. When it isn't, it's bl**dy irritating!
I tried installing an aerial in my loft (no existing aerial here, pretty much every property in town is wired for cable due to anti-aerial planning laws). This didn't help as I am in an area not covered by Freeview according to postcode.
So, I climbed up to the apex of my roof and bolted a mast on. Fitted that very same aerial and now the Freeview works. It gets blocky every time a moped goes past, the (RF) noisy little bu**ers.
1) Try the postcode search at
http://www.freeview.co.uk/.
2) Consider an external aerial if you don't have one already
3) Try borrowing someone else's box of a different make (my box won't pick up at my grandad's house, but my brother's did so he bought one of them)
4) If it gets to the stage where you need to pay a guy to come round and sort an aerial, consider Sky as it may not be any more expensive over a year or two.