Let's start by making one thing clear: TV transmitters are designed to ensure that they provide an acceptable signal to everyone within the relevant area who uses a good-quality
external TV aerial. Since the earliest days of TV broadcasting, there has never been any intention to serve people who try to use indoor aerials. So many people will find that NO indoor aerial can EVER meet their needs.
However, if you want to try using one, you need to look for a high gain figure (which is likely to involve using an amplified aerial) and this is what I'd go for in your situation:
http://www.maplin.co.uk/p/indoor-tv-aerial-with-signal-booster-a38jb