As a rough guide, it is not unreasonable to estimate the hourly rate of an SEP helicopter at 2.5 times that of a similar fixed wing. Plus if you add on IR(H) which has to be completed in a twin engined helicopter at £1,000 an hour, then no, ATPL(A) is cheaper. Conversion then back to (H) is probably a better option.
Cheers
Whirls