The weather may not be warm enough for them yet. They do grow slowly to begin with. Make sure the compost is not too wet. Are they in small pots? Plants don't like to have masses of wet, cold soil around them, that's why you should only pot them into the next size of pot.

They are in 24x40mm potting on trays. I have enlarged the drainage hole in each cell to give better drainage. They are planted in multi purpose compost. I have been feeding with a weak solution of liquid fertiliser last 3 weeks. Thinking about adding some growmore Is this OK?

I wouldn't be feeding them with anything yet....wait until the have a reasonable root system before feeding....keep them on the dryish side until they have plenty of roots.....then feed...

i had mine delivered about two weeks ago and mine aren't doing anything either but its still early days.i have to say i was disappointed with mine from unwins seeds,they said average size 3 inches,theres me thinking im getting a good deal.eeeer no. they were half an inch so they like yours will have a lot of catching up to do before we can both plant them out.like vounteer says is still really cold.