Okay this may sound a bit harsh but frankly it needs to as there are a couple of posts on here that really concern me. Some advice may be well meaning, but if there is one place you never mess with then that's the Inland Revenue. Do not assume that you can claim for things because you think you can, because your best friend tells you you can, or even because the geeks say you can. Go on the Inland revenue course, go and visit your tax office or phone them up and get if from the horse's mouth.
If you claim for stuff that you are not entitled to and get called for a tax audit ... and trust me anyone can, it's a lottery as to whether you name comes up ... then they will not take kindly to you pleading ignorance, or saying that your 5th cousin twice removed used to be an accountant and says you can. YOU MAY BE FINED FOR COCKING THIS UP. Your life will not be worth living!
Please geeks if you don't know what you are talking about then please don't answer, you could end up getting someone into a hell of a lot of bother. The IR do all these courses for free because they want you to get it right in the first place. And just because a dog groomer or lap dancer etc etc can claim for stuff doesn't mean you can claim for it too. You are in a different job and need different tools to do it!!!
I will say it again, DO NOT MESS WITH THE TAX MAN, DO NOT THINK YOU WON'T BE CAUGHT AND HELL IF YOU WANT TO DO RISK IT THEN FOR PETE'S SAKE DO NOT ENCOURAGE OTHERS TO DO IT TOO.
This site is a professional forum and it looks really bad when people, no matter how well meaning, give out advice that they really are only guessing at! Go to your IR office, only they know what is right and wrong.