Trellis in top of 6fr fence

[badgerread]

I have 6ft panel fencing surrounding my garden (apart from the new bit which is my neighbours fence). The neighbour at the bottom left has had an extension done with bifold doors onto the garden. He has just asked my partner if I would mind them putting trellis on top of the fence as his wife wants more privacy. Thing is I think this would look a bit odd as there would be all these panels with only 2 having trellis on top? I also thought there was some sort of rule about going over 6ft? I have also sold my house (not yet exchanged) so my buyers have seen the house with no extra trellis.

See photo, I'm talking about the last 3 panels on the left at the bottom..

No photo that I can see. It's your fence, which is why they've asked you? Just say no, especially if you've agreed a sale. Yes, 6ft/2m is the limit without planning permission. I'd let your buyer know too in case they realise you're selling and do it anyway.