With Chris help, the forgot password link is working! (+1 vote for Chris de Gelder) All I need now is to make the request.getParameter("GUID") a bit more dynamic so the deeplink can be used for other links rather then just the forgot password one. Although, I could always pass the GUID for all deeplinks, and that will work too.
Mainly, I have used the v5+ notation of the "Forgot Password" module, and updated slightly the java actions "StartDeeplinkJava" and "ExecuteDeeplink". The missing bit of the puzzle was the "request.getParameter("GUID"); call to assign the qs value that is then passed on to the required microflow as a parameter. If we were on v5+ this would have been simpler, but when we get that glorious chance to migrate, things will be simpler, as this section already looks similar to the new forgot password module. All good! Thanks. LR.