Deal ending, fix or go on to bmr?

Jkb_2

We have £72,000 left to pay at just under 50% LTV, there's 20 years left on the mortgage and our current 5 year fixed deal ends in July. Do we let the mortgage revert to the bmr or fix it again at 4.09%? It would save us £100 a month on the bmr but obviously that won't be forever, but if we fix it now, we should get a better rate than if we wait.
I also want to borrow an extra £15,000 to do some work on the house and our current provider, nationwide, want to put us on An additional borrowing rate of 5.09%. Would I be able to take out one mortgage for the whole amount if I swapped provider? Or is it better to stay with nationwide because of being able to stay on the bmr?
This is a nightmare, so many questions, and so little spare cash that I don't want to mess it up!
Thanks for any advice you can give me!

withabix

Both the BMR (2.5%) and the HMR (3.99%) are less than the fixed rate.

Personally I would stick with the BMR for now.

Borrow the extra money and overpay (if allowed) by the amount you would be saving by going on the BMR for your main mortgage.

Swapping provider will lose you the SMR rate (you won't get that anywehere!!), but you may be able to get a good deal with another lender due to your LTV.

Minefield isn't it!!