SRD
At present that bit of SERA has an exemption in the UK - we are still permitted to fly low, as long as we are 500' from "any person, vessel, vehicle or structure". And that's a 500' "bubble" around the object so you can be very low as long as you are 500' horizontally away from the object.
500' doesnt look very much sideways I've found.
As I said earlier, any PPL student should expect their instructor to make them do PFLs much lower than 500'. Its the instructor's job to call it off early if the 500' rule looks like its about to be broken - if not and all else is well I regularly go down to 50' or so.
Qualified PPLs should be in the habit of practicing PFLs on their own too.