For those using this site for more than a year – Ethel (where is she now, when I need an argument) used to regularly post that such employment covenants could be enforced by law.
I, in turn, pointed out that this was complete botox – otherwise supermarkets could stop check-out staff (or shelf stackers) taking employment with a rival chain via such restrictive employment contracts.
One reason that the law will have no truck with such nonsense is that the State would have to pick up the unemployment tab, while ex-staff seek employment that their previous employer deem acceptable to them.
Where your previous employer has written ‘and would like to inform you that we have already obtained advice from our legal protection consultancy service on this matter’ – that advice is likely to be that there is f*ck all they can do about you starting any such business, should you chose to do so.