Take into account how much you can over pay without penalty, as they can vary. Check how much that LTV percentage difference actually makes, say the 1.15% vs a 5yr fix at 1.9% (guessing), over the 5yr term. Is that extra money worth the security or not? -only YOU can say. And what's to say you don't have rubbish neighbours during any fixed term, in any area? Moving costs lots of money as you say. Mortgage fees to access lower rates are worth it if they work out lower in the long run too, but that depends on the loan amount, and if paying the fee up front. Without figures it's all guess work here.
The most important question, is this the place you really want to buy?