Just to confirm, this is a new business rather than the incorporation of an existing business within which the van already exists.
If as it sounds this is the straight purchase of a second hand Van from non related parties in an arms length transaction then there is no reason that you should not use the AIA if you need to although as it is your first year be careful that you are not throwing away capital allowances that could be carried forwards against future profits.
Also remember that the AIA is pro ratered rather than being a set figure regardless of the time period. Although, for £2000 I don't imagine that there would be an issue unless you have major expenditure elsewhere.
kind regards,
Shaun.
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Shaun
Responses are not meant as a substitute for professional advice. Answers are intended as outline only the advice of a qualified professional with access to all relevant information should be sought before acting on any response given.