when i switch on the a/c i get a kinda screeching noise, sounds like a fan on steriods and no cold air ..gas in system and normal blowers work...any ideas please.

slipping belt ? possibly the compressor bearings causing it ? When the air con is on it creates quite a load, so any slippage can squeel.

Might just need a new belt, they can get "polished" especially if there has been slip.

the noise isn't in the engine bay but behind the dash...strangely it went away for bit but now has come back...i'm thinking a fan is starting to seize maybe..

hmmm, don't know then....time to get the dash apart ! good luck

if you can get to the fan motor would some of that electrical spray work to lubricate/clean?

something like this http://www.ekmpowershop13.com/ekmps/shops/...-285-p.asp

thats my thinking, get the spray in there and see what happens...