On a separate note if anyone's interested, I've just had a final answer from HMRC about tax relief on Mess subscriptions. Apparently they're not tax deductible because you do not need to be a member of the mess to allow you to carry out your professional duties.
Now that has just triggered another separate but related thought. If the criteria for deductions are that they are required as part of your professional duties, does that mean if an individual maintains their own home but is posted to a unit on the other side of the country and thus has to live in during the week, then accommodation charges should be subject to some sort of tax relief?
After all, very few people with their own homes will do the weekly commute out of choice, and to have a long commute at either end of the day on top of long duty hours presents at worst a potential risk from cummulative fatigue during the commute and at best will see a decline in productivity. Therefore, one could argue that living in and thus the associated accommodation charges are a requirement of your professional duties. Just a thought, may be way off and I'm sure there are far more knowledgeable individuals out there that could clear that one up, but for Grade 1 accommodation that could be a couple of grand per year you could claim against if allowed.