Similar experience with SL - I needed some advice concerning the timber I wanted to buy. They weren't particularly helpful and quoted an enormous figure for wastage - far higher than I've ever experienced in practice. They ended up quoting me 70 quid for some oak I ended up getting from a local sawmill for 20 quid (cheaper cube price and less - well virtually no - wastage). So, for timber I can't see myself using them in the future.
On the plus side, however, I ordered some non-timber items from them recently. They sent an incorrect item, which they cheerfully replaced with an apology, and I had to return an item I couldn't use (I didn't think the website description was clear, they did) but again there was no problem in them taking it back.
They do have some very nice veneer in stock though, so when I get tempted to try my hand at veneering I'll probably go there for supplies.
RP