https://www.amazon.co.uk/BigBlue-Charge ... YXRm&psc=1
Edit 10 minutes later, Pondering complete, bought @ £73.

There are two versions of the 28W big blue available. I went for the older version passing on the ammeter version. The older unit has three usb ports not two, larger better performing panels according to review, is a tenner cheaper and due to the more awkward usb port access has a better chance of getting through a rainshower unscathed.
The amazon review
' I purchased the non amp meter version. YouTube reviews from as back to 2017 show the same Sun Power cells as the latest 2022 amp meter version. So the new Sun Power 36W have the same cells as the non amp meter one I purchased. Anyhow, I had both today side by side, and tested. Amp meter unit with Sun Power cells was useless. Did not even start to charge the iPhone 13pro Max through my window. Meter showed 0.0. The non version started charging the phone through the same window and angle. Very low current @ 0.7A but it seems to have more sensitive cells. I am sending the amp meter unit back and settling for the older model. I thought Sun Power were better cells, seems not. Also the Sun Power cells are smaller in size than the older version'
The guys name is Christopher Emmanuel, his review with photos is a few down in the review list section. Worth a look to see the side by side comparison of the panel size.
https://www.amazon.co.uk/BigBlue-Charge ... YXRm&psc=1
It also gave me the opportunity to buy a shonky aliexpress usb amp meter.

P.S, if you are looking for one of these big blue panels, be careful. The various website reviews are all over the place with regard to the actual specs, text and photos of the two generations. Much laziness and mixing up.