It can be easier to have had a few lessons before taking your theory, it generally means you will have picked up some signs, 'rules of the road' etc without having to learn them as such. Also, as you say the hp part can again be a bit easier with some driving experience. But it is by no means essential! Tbh, the hp part didn't really feel like how you 'actually' drive, it totally focuses on you seeing the hazards. There are loads of cd-roms etc out there with practice clips on them, just keep going through them, there is a bit of a knack to the timing of clicking on the hazards, once you have worked out when you are meant to click you should be ok.
With the mcq questions, you will need to learn stopping distances, have a read through the highway code, and a go on some practice tests and there fairly easy. If I remember right stopping distances are the only thing you *need* to learn, alot of the other questions are fairly straight forward (or at least 2 on the answers are totally stupid!)