Tomatoes gone wild

I bought 4 tomato plants from a large garden centre - Tumbler, 2 yellow and 2 red.  I've had these before but never have they acted like this.  They are "no need to pinch out sideshoots and no need to support" types - they tumble over the sides of the pots (or rather, that's what they are supposed to do).  My 4 are really, really healthy, with masses of fruit appearing plus loads more flowers; however, they are all between 75-100 cm tall and show no signs of either tumbling down or stopping growing.  They're in an unheated greenhouse (as always), watered and fed regularly (as always) and generally well treated.  Anyone else got this problem this year?  And when I put them out at the back of the house (on a south-facing wall in a sheltered garden)  to aid my neighbour when watering when we're on holiday, should I stake them just in case it gets windy?  In case anyone thinks they were mislabelled in the garden centre, they came from the centre of a very large display of Tumblers...so it's not a random case of mistaken identity.