Hi, I have an offer of a fully funded PhD from a UK university. Standard stipend of 13590 GBP is included. My question is that as an international student, will I be reimbursed expenses like air fare, visa fees etc. Of course, I can ask this directly to the University but before that want to know your opinion. Thanks.

I would doubt it. If that was included I would expect it be in the offer letter, but I have never heard of this happening before. Many universities don't even cover the full expenses of permanent lecturing staff moving from overseas.