I was told that a Commercial Vehicle can be charged against tax at the full value of the Vehicle, not for the first year but for as long as you own it?
A non Commercial Vehicle can be offset but only at 10% of purchase cost, and a claim can also be made for the cost of any hire purchase payments, I have been told that this 10% can be charged year on year, plus all running costs, tyres, servicing, up-grade of Sat nav to ensure you are driving safely.
Cost of parking, cost of Road fund license
Bottom line is get an Accountant, one who has several other trades persons on hid books that way the Accountant will have all of the relevant information to mitigate as much tax as he can for you.
You need to have a meeting and if you have the time and are willing you could do a lot of the mundane Donkey Work and provide the Accountant with spread sheets of Parking, clothing, miles travelled [40p/Mile for first 25K miles, then down to 25p/mile] Etc.
Ken.