Its not the same as materials on CIS. Basically you buy the kit, which would be classed as capital equipment.
Normally this would attract a capital allowance of 20% per annum, allowing you to write the asset off over 5 years, however for lease companies such as this, you could claim Annual Investment Allowance of 100%, meaning that you could charge the total value of the asset against your income in year one.
There is a maximum allowance of £1000000 for 2011, but this will decrease to £25000 in 2012.
In general you would buy your kit in year one, and claim the total cost against income received from hire in year one. Then in year two you would have no significant costs so all your income would be taxable.
Hope that makes sense!
Cheers