Yes
flyciderman I'm sure, though a lot of LLs ignore it and pressure the tenant to give them access.
If the tenant refuses to allow a gas safety check all the LL can do to protect himself is to be able to show that he made every reasonable effort to gain legal access. The gas safety check, although a legal requirement for the LL, isnt an emergency and therefore you cannot force entry. There would have to be a complete breakdown in tenant/LL relationship for the tenant to refuse access for a gas safety check though, so in most cases the tenant will sensibly allow access at a convenient time.
There have been a few discussions on the LL forum about how LLs should protect themselves from prosecution for failing to provide a safety certificate in cases such as this here....
http://www.landlordzone.co.uk/forums/forumdisp lay.php?f=3
There is also much advice on that forum about unfair charges, gaining access etc.