Low level helicopter routes over London

[taxistaxing]

Hello,

I live in central London and we regularly get helicopters flying low overhead and hovering. Usually pleasure flights and flights filming shots of the London skyline.

I've noticed quite a few 'single' helicopters - R22s and R44s, in addition to turbine machines.

I'm a fixed wing PPL and just curious as to the rationale behind allowing helicopters low level over London when fixed wing single aircraft are prohibited due to the 'glide clear' requirements. If the engine quit in the hover at 1000 feet how much forward distance could you cover in an autorotation? Less I would imagine than a fixed wing SEP in the same circumstances.

Would you aim to put it into the river if everything when quiet?

Thanks.