Good question about the curved electric rad. I can't say I've ever seen one. A bit of Googling doesn't come up with anything either.
A lot of building, and particularly plumbing matters are fraught with "tradition". Things have moved on. There is little justification these days for siting rads under windows anyway.
In fact, I would argue that, given the potential for huge heat losses through 1930s (or any other) windows, it's probably the last place I would put a rad.
Old-school plumbers still stick to the old ways. The thinking once, was that walls needed to be left clear for huge old sideboards and wardrobes. It's nothing today to put a sofa along a wall in front of a radiator.
Anyway... back to the plot.
1930s house - solid, dependable construction, but with the insulation level of a garden shed - and just as draughty.
Electric heating, even with the modern, German/Scandinavian style panel heaters, is going to be very costly to run without serious alterations to the fabric of the house.
A modern, high-efficiency gas combi boiler is still probably the best option. They are due to be outlawed one day, but until then, the CO2 Police are not going to come along and confiscate them ;o)