Can anybody identify this greenhouse pest, from its description and suggest the
best remedy.

It is white, but about 3 times larger than the usual white fly.
It preferred the tomatoes plants last year.
It fly's straight and very fast.
It now prefers (with there being no tomatoes) geraniums to pelargonium, and
then fuchsias.
It has the appearance of a very small grasshopper and the closest picture I can
find is this, but remember it is pure white.
http://www.pozosur.com/ingles/plagas/plaga_trips.gif

Hamish