No precise date but try http://en.wikipedia.org/wiki/Maize 

 Is there much grain maize grown in the UK?

Not a huge amount Tas, at least not compared with France et al. According to DEFRA June 2007 statistics maize accounts for 130,800ha last year (up 5%).

 In comparison wheat totals 1,693,000ha, barley (all) 566,400ha, oilseed rape 564,200ha, potatoes 105,300ha, sugar beet 122,200ha, beans 116,000ha, peas 34,500ha

 Most of the maize will be fodder, with a small proportion of grain maize.

What type hybrids are they ie 85 day, 100 day, what maturity I guess I should ask.  When they are harvested for grain, what is the yield? We saw corn as far north as Stirling in Scotland on our trip in late July early August, I must say that none of it looked very good at the time, I suppose not enough heat units and too much rain.

 Thanks Mike

Only grown for silage here in Tassie, I dont know if it has been tried for grain here or not.