Apple trade-in for gift card website issue

I’m trying to trade in my Apple Watch Ultra for a gift card via the website (uk). I’m not looking to get money off a new one as I have already upgraded through EE; whilst they also offer a trade in scheme, Apple offer a greater amount.

The issue arises when I go through the process of inputting the serial number, answering the questions on its condition and finally giving my name and address, etc. every single address I have tried, every permutation of those addresses and none of them work.

It comes back with 'We're unable to verifiy your address ad maynot be able to complete your trade-in if it is incorrect. Please confirm if the address you entered is correct or edit it.

Im only given one option though, to edit. There appears to be no 'Confirm' button. On occasion it will say I have an option to use a recommended address and the button for using the recommended address just brings me back round to editing my details.

My home address is correct with our mailing service, I’ve had no issues before now with the likes of banks, retail purchases and even my Apple ID is set to this address. The other addresses I have tried were family members where some of those live in a large city (one of which a stones throw from an actual Apple Store) and some work colleagues who live in the same area as myself. None of them work.

I would just go visit an Apple Store and trade it in there however this would involve an 12 hour 200 mile round trip involving several busses and/or trains which ultimately would cost me more than the gift card is worth.

I also called Apple support them selves and after 45 minutes of explaining my issue to 3 different people, none of who me asked for my address to try and do anything or even asked for any details from myself other than an order number. They all seemed perplexed that I wasn’t trading in whilst purchasing a new product and had absolutely no knowledge of my issue or how to fix/work around it. This is despite seeing multiple other posts in the community asking the same questions as I.

How do we fix this? Why is there an issue? And how do I trade in my watch for the gift card and do a little bit to help the planet?