I finally got a reply from T&M, so in fairness to them I have copied it below.
I like the "further assistance" offer and I'm rather tempted to ask her to come and peel the long ones for me, but that might be construed as being a tad childish.

We thank you for your recent e-mail and were sorry to learn that an error had occurred during the packaging of your seeds.
In order to maintain the high standards which we pride ourselves on, we carry out quality checks throughout the packing process, so errors such as an incorrect seed rarely occur.
We understand the disappointment you have experienced and have arranged for a replacement packet to be sent to you free of charge under separate cover. We feel confident that these will enable you to achieve maximum satisfaction from our product.
You are correct about F1 hybrids. They should produce uniform sizes of fruits and the bendy ones certainly were not the usual Harrier variety. Unfortunately we have not had a reply from our vegetable expert about the identification of the particular variety which you have grown. It is not within our product range so it would appear that there was a collation error and a couple of rogue seeds must have slipped in from our supplier.
Please do not hesitate to contact me if you require any further assistance.
Kind regards,
Anne Watson
Customer Care
Thompson & Morgan ( UK ) Limited