155 Man.
It's my experience that such things are entirely at the discretion of ones employer, who will reserve the right to change his mind as and when he pleases.
http://www.pprune.org/forums/images/smilies/evil.gif Besides... "It's to pay for your expenses - not to make you money !!!
http://www.pprune.org/forums/images/.../eusa_wall.gif But seriously, if anyone does have any experience of a UK company paying per diems or similar allowances tax free please post it!
Cheers