FYI current 10yr Market Rates are around 3.95%.
The question of whether to Fix or Float depends on your attitude to risk. If you prefer to know exactly how much your payments are going to be and not have to worry about the effect of German unemployment/inflation etc on your mortgage rate, then fixing is probably for you.
You can plan your finances/savings/investments in the knowledge that your mortgage isn't going to change.
Of course, this certainty comes at a price. The long-term fixed rates generally work out more expensive than the equivalent variable/tracker/shorter-fixed but you have to expect a premium for the stability they afford you.
I wouldn't worry too much about fixing the rate before Dec7th - this rate rise is 100% priced into the market (indeed, it has been for the past few months) so there shouldn't be much change in the Mortgage rates.
Personally, I don't like long-term fixed rates because it can sometimes be difficult to pay down large sums off your mortgage whenever you receive a lump sum (bonus, SSIA etc). In a rising rate environment there should be no 'break costs' (other than maybe admin costs) since the bank can lend the money again at a higher rate.
The problems really start if the rates start to fall again at some stage over the next 10 years. If you look to sell the house/redeem the mortgage to switch to lower rates, the banks claw back the break cost - the difference between what they would have earned from you over the remaining term and what they can lend the money at now. This break cost can often wipe out any savings you might make by switching - or it can be an expensive extra cost when you go to sell.
Take a look at the thread above - some of the posters expect v high rates over the next 2 years, in which case 5% fixed would seem an absolute bargain!