I certainly wouldn't "gamble" on the variable.
You've already heard from the horse's mouth that they're gonna raise interest rates by 1%, and every man and his dog reckons the ECB is gonna start increasing interest rates twoards the end of the year.
So the only way interest rates are going, is up.
If you can, fix it for the 5 years, and give yourself some breathing room. During that time, if you've an extra few quid, throw it into a saving account. That way, once you come off the interest only in 5 years time, at least you'll have a few bob to throw against the principal so repayments won't be as steep as they could've been.