No basically.

Last week I tried after landing at Terminal 3 and the guy was very adamant that they weren't accepted - when I pushed it he "tried" then after a few minutes of counting cash piles he returned it to me - said it didn't work and told me to go around the corner to the ATM the return directly to the front of the queue and see him again.

On my return (into Terminal 2 this time), the couple in front of me tried and were told to use an ATM right by the booth. (I had converted cash before flying)

They will take USD / GPB / EUR and even offered THB although I think the conversion rate was rather arbitrary and certainly in their favour.

ATM is close T2 around the corner towards the Egates - T3 just by the booth. Also, once you have your EVOA you can use Egates - no need to queue in the manual queue (with a UK passport anyway)

Hope that helps!