 BRITaIN needs more television gardening programmes to cater for the increasing number of people who want to grow their own fruit and vegetables, according to a presenter of Gardener's World.  Speaking at the Telegraph Hay Festival, Carol Klein said: "It is seen as a minority interest and therefore only deserves a certain amount of airtime, when in fact I think it is very major. There are 11million gardeners in this country and nearly everybody has something to do  