I nip the side shoots out till I am left with 5 and keep nipping any that appear after this.

There are two types of tomato plant: determinate and indeterminate.
The former grow naturally into bush types, with fruit borne on every sideshoot, and if you try to pinch out all the sideshoots and grow as a single cordon it won't usually get beyond two or so trusses. This is the sort you seeing growing in the fields in Italy which are harvested by machine.
Indeterminate tomatoes (which are the majority you find in the seed catalogues and garden centres) are easier to keep under control as you can grow them as a single 'cordon' by pinching out all the sideshoots and the plant keeps growing longer and longer, which means in ideal conditions you can get numerous trusses of fruit over an extended period.
If you want small bushy plants I would definitely choose a DETERMINATE variety, or bush variety, as these as particularly good for a lot of fruit with an early crop. (But they come all at once with few later ones).
Many of the Italian type are of this sort, but look out in the catalogue for the description. As Drc726 implies above, you can treat any indeterminate variety as a bush too, by pinching out the main growing point and fruiting them on the sideshoots, but you might have quite a battle keeping it under control. You don't want all leaf and few fruit, and the more sideshoots in general, the smaller the fruit on the indeterminate type.