Single engined. Planned powerplant was a Rolls-Royce Merlin "mounted in fuselage driving
wing-mounted propellers", no further info available at the moment.
Speculation: given the timeline, it's likely that the intended powerplant was the Merlin I, although it is also possible that it was originally designed with the Merlin E (Merlin I was also known as Merlin F) in mind, although there wasn't that much difference between the two types and the earlier developmental Merlin C. Specs for the Merlin E/F included generating a constant 955 horsepower (712 kW) for 50-100 hours and a maximum rating of 1,045 horsepower (779 kW).
Minor Health Warning: I didn't feel like looking up my books, so I used the Wiki article on the Merlin for a reference, but I think it's accurate enough.