I'm sure that his NOC did NOT make a 'mistake' when saying it would be an extra 90 per month - take a good look around at many of the places offering dedicated server rentals. With the majority of them, if you do not upgrade the RAM immediately when ordering, they will charge you a monthly fee to upgrade it. I know, it's ridiculous and stupid because you end up paying for that RAM over and over again every two months or so, but that's what they're doing. Again, one of the reasons I got into hosting - the hosts just screwed you any way they could, even if it was horribly apparent and overboard. This behavior is not restricted to just hosts, I've found... the NOCs do it too.
I would hope that 90 per month "extra" would be a mistake - as a memory upgrade is a one-off cost! Also for the price they were charging as an "extra" cost you could probably lease and host a new RAQ for that sort of money!
BTW, a Micron stick of PC133 RAM 256MB is running about $69 USD here retail, a bit lower on the wholesale end (like on Ebay or the computer trade shows). No idea what that translates to in pounds, and truly no clue on what "VAT" is (other than something you put brewing ale into...)
The exchange rate is approx: UK£1.00 = US$1.42 (see: http://finance.yahoo.com/m5?a=1&s=GBP&t=USD - so US$69 is nearly £49 - expensive! See: http://www.crucial.com/store/PartSpecs.asp?imodule=CT32M64S4D75 - US$39.59 for the same memory you quote!
But I would just go to: http://www.crucial.com/store/ListModel.Asp?MFR=Cobalt+Networks and choose from there.
Just to answer your other question - "VAT" stands for "Value Added Tax" - basically a sales tax added onto the price - currently 17.5% - so now you know :)
BTW Crucial is a division of Micron and *NO* I have nothing to do with them - just find their memory to be low cost and reliable. I would also watch as the one you quoted is a PC133 when the RAQ's actually use PC100 (although it would probably still work - but not being a memory expert I could not vouch for it).
Thanks...