Why are my sweet pea flowers short and stubby?

it depends on the variety. if you remove the tendrils it wont self cling nor climb. If you want really long stemmed ones chose an exhibition variety next year. this is also true about scent, some have more than others.
welcome to GoY too.

It might be the variety you've chosen, as Seaburn intimates above - unless you're growing them in a container - depending on the size of the pot, that can mean no flowers at all, never mind short stemmed ones. Cutting off the tendrils will make no difference to the length of the flower stems.

Thank you both. I bought a packet from the pound shop and inside were 6 packets of different varieties - all 80 odd plants came up and they are growing either in a couple of large tubs or around the garden where there is room. There are six different colours and they smell lovely - just shame about their shortness of stem.