Even without an Eastern front, after the Battle of Britain, there is nothing to knock the UK out of the war.

The question would hinge on wether or not a drawn out war would deprive the Brits of the desire to fight, not the capacity. If so, then yes. If not, then a British victory would still be a certainty.

Germany's ability to wage a long war was incredibly limited whereas the Brits had the rich resources and help of its empire to sustain it.

Such a conflict would mirror the Anglo-French conflicts of the 19th and 18th centuries.