However, follow this guidance and you can afford to be a little more generous with your customers this year:
Small gifts which carry a conspicuous advertisement for the trader are an allowable expense. Common examples include: branded diaries, pens and mouse mats. The advertisement must be on the gift, not just the wrapping.
Unfortunately the expenditure of the following kind is specifically excluded (even if it incorporates your advertisement): Food, drink, tobacco, gift vouchers and gifts exceeding £50 per recipient (even if it carries your business logo).
Source material: http://www.hmrc.gov.uk/manuals/bimmanual/BIM45070.htm
Enjoy saving tax?