Finally I managed to get my wheel alignment done. Tony from WIM was kind enough to supply the values he suggested would be best for my car so I could save a massive trip down to Buckinghamshire. I ended up having it done in Hull by Just Car Clinic, who have a 4wheel geometry wheel alignment machine in all their branches, which is good to know. Despite this, at first they set it up very badly, with the steering wheel pointing very much to the right and the feel of the steering ruined completely, claiming they couldn't do any better because a bend in the suspension of the OSF wheel. After this I consulted with Tony, who, again, completely free of charge, out of the kindness of his heart advised me and even gave me his number to call him if things don't get fixed. When I took it back for them to have a second look, they took 2 hours, instead of 25 minutes, like before, and they managed to set it up very well, despite the little bend in the OSF suspension. Now the car feels very planted, very well balanced.
I have to say, huge thanks to Tony at WIM for all the help throughout this ordeal, without him I would still have a wonky steering wheel and dead-handling car. If you live anywhere in the south, there is no better place to go than WIM, support their great work!