I expect it is the ECU failure.. I have a 95 +4 and had a similar issue, a new / replacement ECU fixed it..
Where in Kent are you? If you were close you could try my one but expect you have an immobiliser which might make that problematic...
It is quite common for the ECU’s to fail.. What’s the code on your ECU if you have a look on eBay you might find a cheap replacement, alternatively there is a places that will repair / replace it for about £100.
