Wireless cat fences - anyone got one?

[beachbodhi]

Hi all , I have 2 beautiful kittens and a massive garden for them to play in when they're allowed out -there is a busy road the other side and I'm starting to feel panicked about something happening to one or both of them . My children have become very attached and my youngest with autism (non-verbal) has been using more words and engagement with them. So it's been wonderful and we love them dearly.
This has all got me looking online for options -we couldn't have proper fencing as it's a grade 2 listed house . The garden is probably the size of an Olympic swimming pool with trees and surrounded by thick hedges. I've made enquiries with one company that lay a wire in the ground that lets if a buzz on the cats collar if they try to cross -it's an FM frequency thing that doesn't shock them.
Has anyone any experience of reviews for this sort of thing ? Or alternative methods of keeping them in the garden. Thanks x

[bodgeitandscarper]

You can get freestanding enclosures to cover large areas, meaning that nothing would need to be attached to the fences. No idea on whether you'd need specific permission if an aonb, but if fruit cages are allowed then there isnt a great deal of difference.
As for tracking collars, we had one and gave up after the cat kept losing the collars and expensive trackers. We tried a harness, the cats hated it. Our best solution was a catio which I use for the indoor cats. I know that this is something you dont want to consider, but it is probably the only thing guaranteed to work.