I want to reply and argue it but my husband is furious with me so I am going to reply without him knowing. Surely it’s their issue and I will push for them to sort it, even if it means they go through their insurance. I can’t afford to sort the trees and they obviously can.
Kindly, OP, as someone said upthread, you’re spiralling. Your stress and your resentment towards them for selling you a house you hate is causing you to behave irrationally. Despite being told by your husband, by solicitors, and by countless people since the beginning of this thread that the vendors cannot be held responsible for a property they no longer own, you’re choosing to keep expending energy on a misguided crusade that’s going to get you nowhere.
Unless they have failed to disclose an existing dispute over the trees (which they did not, as they offered to remedy the problem prior to sale), they have no residual obligation to sort out anything whatsoever. The fact that they can afford it and you can’t is neither here nor there.
Property transactions are caveat emptor - ‘buyer beware’ - and it’s your responsibility to look into potential issues prior to purchase because on completion those issues - whether it’s remedial work to the house, or disputes with neighbours - pass to you.
Plus you keep talking about subsidence as though it’s a proven issue, when it’s simply your neighbour’s opinion (and probably, as other PPs have said, just a way of trying to make you cut down trees they don’t like). Until they produce a report by a legitimate professional that indicates their home is subsiding and that trees on your property are the cause, they have no power to force you to do a bloody thing.
You seem fixated on pushing against a brick wall (the previous owners and their legal advisors) for a resolution you’re never going to get, when the far easier option is just to tell the complaining neighbour to pipe down and leave you alone until they can produce legally sound evidence of subsidence (which they almost certainly won’t). Just say you like your trees and if they keep approaching you about them you’ll consider it harassment.
Then direct your energies elsewhere. You’re just hurting and exhausting yourself by continually running into the same brick wall and getting the same result.