easyJet and KLM fly AMS-BRS. There are many other 1 stop options from AUH to BRS.

However, you have provided no information about what points/miles you have and in which programs so it is hard to give any further advice. I would suggest you first compare cash ticket prices, then look at what options your points/miles can be used for on which airlines and check their award availability.

Note that from LHR it is under 3hrs by train to Weston-super-Mare, from BRS it is over 1hr by bus/train. Personally I would look for a direct AUH-LHR flight and take the train, or instead rent a car from either location.

Is your plan just to fly to the UK to visit Dismaland and then return to AUH?