40 minutes worth of grass to cut.

-- Well that's a different measure of a lawn.
Mine used to take around 3 to 4 hours to cut with a 20" cut, now have a
1.15m cutter bar and cut a bigger area in 45 mins.

Have you thought of a small petrol mower a lot cheaper and easier to find
than a rechargeable electric mower.
Rechargeable/cordless electric are available but are expensive and don't
have a very long cutting time against a longish charging time.
David Hill
Abacus Nurseries
www.abacus-nurseries.co.uk