I would go to the small boutique in Manchester first and see if I could hit it off with an SA at that boutique. My experience has been that small boutiques get plenty of stock so the relationship and liking the boutique would win over heading to a larger urban boutique.
Thanks for taking the time to reply Cravin. I think that sounds like sensible advice, although I'm not that close to Manchester it's more convenient than London. I have heard good things about the staff at the Manchester store on threads I've read as well which is nice. I can always compare with another London store next time I visit, especially as UK H staff don't work on commission it's probably less of a big deal only using 1 SA or store than in other countries.