Cheers for the offer 4F, but I've just opened the lidl tool kit (which I bought for my dad and brother for this christmas hohoho) and there is a tool in there which looks like it does the job - they won't notice if I give it a little clean afterwards! Thanks 4F, you've been a great help - I'll give you a shout if my tool doesn't do the job.
LBS wanted £25 for the BB and £15 to fit it! pffffft.
No problem, That will work fine, it's the same tool kit I got