wouldn't like to say for certain but the odds seem against it. it's not mentioned among the 'Saxon' occult thrillers at back of any Five Star i've seen and i note Sev leaves it off his listing. but if ever you find one, do let us know.
From the first, I set myself against "literature"; the story was the thing, and no amount of style could persuade me to select a story that lacked genuine, unadulterated horror. For those who wanted something high-brow there was plenty.
I aplogize if I state the obvious, but on Amazon marketplace UK are a lot avaiable, also on Bookfinder com . And after my experience some of the american marketplace seller sell overseas for the fixed postage. You just have to click through the cart menu to see which one delivers outside the country.
The US edition seems to be pretty common in the UK, which may be why there was never a Five Star edition. When I recently ran a search to check if I had them all, I found more copies of the US Rathlaw paperback for sale in the UK than of any others in the series in any edition. It's a shame, as it means it's not possible to get a perfectly matching set.