do you have any outside access? like a porch or even a large window sill? if so you can grow your grass outside. i have found that growing the grass outside produces a heartier, more flavorful grass since it is fed by sunlight and rain. just dont put it in direct sunlight, wheatgrass prefers shade and indirect sunlight. not sure where to get seeds in the UK as i live in the US, but i am sure a google search would help.