Still think Stansfelds sound like a good bet. Free delivery on orders over £50, and you don't have to be in to receive delivery, as they will leave it round the back or whatever.
I am now wondering if I am spending too much too - I just bought 700cm of 60mm hollow box section (3mm wall) and it was £55 - is that ok or is that expensive?
I used J Doyle Ltd (01204 527008) in Bolton many moons ago when i was working over there. They offered a friendly touchy-feely service, and will cut while you wait sort of thing. (I still have their number so they must have been cheap/good/fast/sexy lady on front desk - Delete as appropriate!) As i said, have not used them for a bit, so don't know what they are like now, but worth a call?
Very few places will turn away a paying customer, trade or not.
Let me know how you get on.