Dont bother with Umbrella companies- you end up paying all your tax with feck all write off's AND you pay a comission fee every month
Just set-up your own Ltd company and keep receipts for everthing (and get a bloody good accountant).
For instance I cant drive, so I get a taxi to and from work every day, but I can write it's all tax deductable in Ireland so it takes a massive whack off my Tax bill end of year..
Not that much is applicable, but transport and part of your milage is one thing, running costs of your office another etc...