Spoke to my accountant regarding claiming, and his answer was, 'you can claim 40% of the value of a 'new' purchase, van, computer etc'. The definition of new, is new to you, not necessarily a brand new item. This is assuming that you use the item solely for business use, otherwise you can only claim a percentage of the business use, after deducting the 40%.
i.e. Van cost = £!000 and is used 50% for business, 40% of £1000 = £400, divided by 50% = £200 claim.
Hope you understand.
Dick