Can't believe this thread is still going!
When the OP put up the original request I read the rules on the tristar website, read the FAQ and in about 15 nanoseconds had worked out a) I wouldn't need a med cert since I am a licensed athlete with my BTF licence b) how great paying my annual membership to the BTF is for all the hassle it saves and benefits it brings both home AND abroad
In the amount of time this thread has been running you could have probably signed up with the BTF, got your membership number (they confirm on payment receipt, well did in my case anyway) and licence would probably be on the way, taking away need for medical cert as noted in the tri star rules...
.... Of course you could just continue to post random opinions against the help of seasoned international triathlon participants and BTF members
Or you could always phone the organisers or the BTF if it's still not clear