a good friend of mine is a patent adviser for a well known company.
He pretty much said this.
If you going to patent something remember once you start the process you are ADVERTISING your idea to the world, as it then becomes public...
If people then decide to contest the idea you can end up spending a lot of money trying to word the idea so that it passes through the patent office, but by doing so the patent becomes weaker as you have to admend it.
Once passed you are protected, 100% nearly.
Question is, can you defend it? can you afford £10ks of pounds to defend that idea through the courts? taking years of mitigation sometimes to get to the actual issue, ie stole the idea ...
If you believe in the idea enough then dont be put off, but be ready though to have to fight for the idea throughout the whole process and be ready if need be to spend £10ks to defend it.
The good story is, once your patent has been defended once it has a very good chance of never going to the courts again as a defended patent is worth gold compared to a un-defended one...that is the biggest advantage of a patent, having it defended once allready.