I'm employed in the uk as a site engineer (industrial refrigeration/ cold storage) i'm based on one site most of the time.

a friend of mine told me that as i buy most of my tools myself i should be able to claim some sort of tax rebate or tool allowance, he said he last done it a few years back when he was still on the tools and he back dated it for a no. of years and ended up with over £600

how true is this

and how would i go about claiming it? as i dont normally get a tax return because i'm salary paid on a P.A.Y.E.