Hi HammerofPompey and welcome to the forum,
Unfortunately being the subject of a photograph gives you virtually no rights over how that image is used, unless it was taken in circumstances where you had a justifiable expectation of privacy, for instance while you were in your home. This category of intrusion is covered by Article 8 of the European Convention on Human Rights (ECHR) as brought into UK law by the
Human Rights Act 1988. And assuming that the image doesn't infringe your Article 8 rights, you are no more entitled to just use the image without permission than anyone else is.
That said, most picture agencies such as Alamy usually insist on a release being signed when a recognisable person is prominently featured in an image submitted to them for commercial use (see 'When do I need a model or property release?' on
this page from Alamy's Contributor FAQ page). This is not due to privacy or GDPR, but because it is possible that a client of the picture agency might use the image in a way which implied that the person portrayed was endorsing a product, idea or activity which the image was used to illustrate. This might leave the agency open to claim for defamation or passing off. Both these are remote possibilities, but the agencies tend to cover themselves just in case.
However your reaction to the demand for £1400 is entirely justified. If you decide that you want to settle, we suggest you counter-offer with the amount that the actual image licence would have cost, since that is the amount of damages a court would normally be expected to award in a straight forward infringement case.
Here's an
article about American model Gigi Hadid being sued for using a photograph of herself taken by a paparazzo, on her Instagram account without permission. There aree two things to note about the case. First, it happened in the USA so the law is slightly different there, and secondly, she actually won on a technicality. Before you can sue for copyright infringement in the US Courts you need to register your images with the US Copyright Office. The photographer in that case failed to do so before filing the claim with the court, and so the judge threw out the case. That wouldn't apply in the UK where there is no requirement for registering to obtain copyright protection.