The injector has o-ring but the fuel appears to start pouring from the regulator not the injector, so this is unlikely to be the cause.
If the regulator's diaphragm needed replacing, one option might be to search ebay for 'Single Point Injection Unit' and find one that looks similar. Plenty of other cars used these Bosch units in the 90s, like this one....
http://www.ebay.co.u...m//361365242330
... £30 isn't bad, but even so, I'd be tempted to make a low offer on this as there isn't exactly a huge demand for them. You should only swap the diaphragm and not the spring as other units could have different springs for different fuel pressures
While I don't like replacing failed parts with unknown used ones, there aren't many other options. If you can't a basic part like that new, then fingers crossed it has very little spares demand and a very low failure rate, so worth chancing a used one.