Building regulations

Not as far as I know. French drains are often used to resolve problems but make sure they are done properly

It depends which area it’s in as different borough have different rules

As long as the French drain should do clear unwater problems

In the UK, local authorities may have specific requirements for the outfall of a French drain into a ditch or watercourse, I’d certainly enquire with your local Building Control Office if you want, they will probably say you’ll need to notify your water company if your sending it into an existing drain. As long as it’s properly installed and surrounded by 10mm gravel to 150mm thickness,you’ll be fine. More to the point, what’s going on your hard standing? You won’t be able to build anything major, like an extension. You’d probably get away with putting a garage or shed onto it or patio.