Was the Austin 7 fitted with a overhead valve aluminium block with steel liners engine? I think unlikely, not quite like the Coventry Climax engine used in the Imp, but it was for the time an unusual engine to find in a car.
What I remember about the Regal engine was you had to undo the right hand engine mounting and jack up engine to renew the oil filter. And would need to bleed the heater to get it working, and it would only work for around 50 miles before needing bleeding again.
They has a leak off pipe to drain petrol if you flooded the engine directed directly onto the exhaust pipe, many caught on fire, and all the resin would burn leaving all the fibreglass lying on the chassis.