Personally, I feel its usually not worth the premium and rigidity of 5 year fixed. 2 year or 3 year usually can offer value in a rising rate environment, but its all about timing. If you are on a tracker at 3.60, then you are effectively going to be on 3.85 in 2 weeks time, as ECB have given all the necessary signals to the market for a 25bps increase.
So, if you can fix at 3.85ish, then worthwhile. Unless the global economies meltdown, then we are unlikely to see a 75bps reversal in rates back to an ECB rate of 2.0% which was as low as they went post 9/11. I think ECB mantra of inflation control at 2% leaves a floor on real interest rates at 2%.