I absolutely wouldn`t buy from Halfords.
The last time I went in I got run over by a couple of the pimply youths they employ racing push-chairs around the store.
Prior to that I asked why their catalogue showed differing size wiper blades for my daughters Polo depending on manufacturer, and which is correct? "Dunno,buy the cheapest" Right.
And when we went to buy an MP3 compatible unit for the same car I gave up after 15 minutes as the `assistants` were all too busy joking with their chavvy mates (who weren`t buying anything) to talk to anyone actually wanting to spend 150 quid.
It`s obvious that this lot are in Halfords as they are otherwise unemployable.
I would suggest going to a decent independent store, they will be able to answer your questions in an intellegable manner and will actually appreciate your custom.