Can't recommend any specific make or model, but as you are buying one, I would advise you get one with twin recievers - come the analogue switch off, you will then be able to watch one while recording another.
I'd also advise against getting a top up TV box - it may be cheap when you compare it to sky or cable, but in my opinion, it isn't even worth what you do pay.
Regarding picture quality, I think this depends on your aerial and where you are - I don't have any problems, apart from maybe when it's stormy, but then I had that when I had Sky.