I can't answer the question, but I can offer
Warbases as an alternative. I've seen these guys around the shows and very friendly they are too.
I can't recall Sarissa off-hand, but I can't say I've heard anything bad about them either. The £2.50 seems to be a flat postage rate, which is then adjusted as required. Postage is free worldwide on orders over £50 ... which I suppose is a lot of bases though.