There will be no problem in training with a Class 1 OML and there "should" be no problem in being employed with a Class 1 OML unless you are looking to be employed in the very few situations which are single pilot. A Class 1 OML is after all only the medical equivalent of the MPL which is the aspiration of many new trainees.
The CAA Medical Division will try very hard to help you obtain an unrestricted Class 1 and if you have an opinion from an esteemed cardiologist which will provide additional confidence then tell them so.