I am trying to convert an area previously covered by shingle into grass with
a flower bed on either side. after digging up the shingle I discovered hard
clay, with large large pebbles underneath. I have turned much of this, and
removed much of the stones. I have been trying to improve the quality of
the soil, so that the flower bed would be useable by adding multi purpose
compost. I have read that adding gypsum helps to soften/ break up the
clay. When I went to Wickes to get this they look at me blankly.... can I
just but 'finishing plaster' or does this have cement in it already?

any thoughts on the improvements I should make to help my tomatoes grow well
once I move them outside.

Thanks
Bruce