So, just some basic information on what was offered.
On an outstanding mortgage of £47k I have been offered 10yrs fixed at 2.39%, so paying back £52,920 over the term with £0 upfront transfer costs.
If I was willing to lock in for just 2yrs I could get 1.69% with £1k arrangement fees or 1.99% without.
The question I'm answering as I'm sure many experts are too is what will the interest rate be in 2yrs time - is it worth me saving <1% in interest for 2yrs; but then finding I cannot get 2.39%
This is really a form of gambling. It depends how risk averse you are. If you take the option that rates won't get any lower the difference between the 2 rates of the 10 year period is £1021.
So the 2.39% 10 year fix will cost you a 1K more if interest rates stay the same for the next 10 years compared to being able to renew at 1.99% with no fees for the other 8 years.
Now as there are thousands of variables given that interest rates could change every month, but probably won't you can't realistically check them all.
But say in 2 years time the best rate was now only the same as the 10 year deal and this carried on for the remaining 8 year. 2.39% that 1K loss would now be reduced to £370.
If best rate was higher at 3% for the remain 8 years then that 1K loss would turn into a £634 gain over the variable.
These example are pretty basic, but give you an idea of the range of costs small rate changes can effect how much you pay.
Psycho Sonny suggestion of a 5 year fix at 2.09 is a good compromise and does make some sense if your not completely risk averse.

If after 5 year you could only get a 3% deal for the remaining 5 Years you'd still be just over £200 better off.
If they hit 4% after 5 years then you would have lost out by around £450 compared to the 10 year fix.
Interest rates could go up if inflation starts to climb. With Brexit happening that is a possible, but no one knows for sure as we have never had a Brexit before to compare to.