Have you looked at these? http://www.metals4u.co.uk/
Don't know how their prices compare with ebay, but if you buy more than £75 ex VAT they do free delivery.
Buying online is not the best way to save money were steel is concerned,I weighed it up that ebay was way over the price by as much as £10 I went to my local steel stockist which is only a mile or so and could make a £15 saving depending on the amount of box section?
Checkout steel stockholders in your area? and offer cash payment,you'll be suprised how much saving you can do.
Yes, I ended up buying from a stockist some miles away from me, but well worth it. Good friendly service, helpful, and about 1/3rd cheaper overall, even costing the fuel in.