I had already upgraded to business class DOH-LHR with miles and went to Qatar's Bangkok office to ask about a paid upgrade from BKK to DOH. They explained it was US$400 payable at the airport check in. (Goes up to $900 from 17.12.08 for "Peak Season")

Anyway I changed currency so that I had the US$400 in cash to pay at airport check in. Was then advised it had to be paid in local currency so was marched to the nearest exchange counter and got Thai Baht. Was then advised it was 14,500 Baht, 800 Baht more than I had just got for my $400. Qatar use their own exchange rate. Fortunately I had just enough cash to make up the shortfall but thought I'd just make others aware.

The attitude of Qatar airways staff was to make the whole process as difficult and time consuming as possible. Almost seemed like they didn't want to allow the paid upgrade.