Thanks G/B, that makes a lot of sense. There is a bit of information here http://www.manleymere.co.uk/water-sports which suggests that the shop has been active since 1984. Although mountain bikes no longer feature, based on your recollection they would have done in the late-80's. The phone number is similar to the odd looking one on the frame sticker (maybe some changes to the format occurred, though I can only recall the addition of a '1' in my area). That seems to solve the question of where the bike originated. I bought the bike from Warrington, so quite local. Great stuff.