Wow, I must say as a very regular user of T&M that I have always found them to not just be good with issues/problems/complaints, but exceptional, for instance, please accept our apologies, replacement plants and a money off voucher for good measure.
I think we can bacome a bit to obsessed with following growing advice to the detriment of common sense and trial and error. In my 3 years of ordering potatoes from T&M, having the same delivery time as yourself, I have never had any issues, but I have had good crops! As stated, simply pop them in an egg box, I cram mine in, and plant when you want to. It's really not that big an issue, they'll grow on just fine. In fact, last year was so wet, that I had them in egg boxes for 4 months before they were planted out, which yes, I know is not good practise, but point is, they grew and I've still got stored potatoes now.
There is of course one other thing that could have been done, or at least could be done in the future, and that's to order later, so they arrive more or less when you want them.
Try Lady Christl, their amazing.