Hmmm... Off the top of my head, chronicle and document the relevant facts, although I don't think there are necessarily any specifically set out penalties/remedies for that.
Legally any violation would stem from your right to "quiet enjoyment" / "peaceful enjoyment" which evokes the human rights act (British implementation of the European convention on Human rights, kind of like US's bill of rights) so taken quite seriously, which a landlord must respect including by giving "reasonable" advance notice of any visits. However... i feel like it's not precisely statutorily defined anywhere and that there are various different schools of thought as to how that legal term is quantitatively interpreted, from about 24-48 hours, though from the letter I sent you it seems like it would hardly be unreasonable to insist on 48.
In this case it sounds like she did give reasonable advance notice and prearrange the visit, however she failed to disclose either one of the purposes of her visit or possibly the true purpose or nature of her visit.
I don't see that as heavily impacting/damaging you other than if the true nature of the visit actually caused her to stay longer than you'd been given an impression that she would. I mean how did the deception/failure of disclosure regarding the purpose of her visit adversely affect you or affect Scott's day?
If it did then theoretically you could sue her for damages that would try to quantify that damage due to her violation of your peaceful enjoyment, apart from the fact that it is in itself from what I can tell quite minor if any adverse impact at all, so a court might decide that no damages are due or not hear it, or just award accordingly negligible damages so that pursuing them wouldn't be worthwhile.
More likely it would form part of a pattern or tendency of behaviour of disrespecting your rights and enjoyment of the property which you're entitled to, and if there are ever any more egregious violations that carry defined and more substantial remedies clearly defined in law, like anything to entice or attempt to make you leave or worse, then this episode might become more relevant in depicting the generally insincere and vain character of the landlady.
What do you think was her motive for telling you that her purpose was something different than it was?
And obviously you should challenge/confront her about that, because as a matter of basic decency deception/lying is always contemptible.
And sorry that does actually sound a bit worse than it was in my mind upon rereading it. Idk I'm still not really fully awake, sorry