There's a few comparison sites for phone recycling - I checked just in case I only get low-ball offers for my 7 Plus (which I've priced at £350) and some of them had valuations as high as £318 although I expect they'll try and find any way they can to knock that down further. Mazuma wasn't one of the better ones (£230!).
Thanks for the tip, never thought to check comparison sites, best is sellmyphone offering £520, same as mazuma (didn't see them listed on the site I checked) was before the announcement (£500 now). I trust mazuma as have used them for years.