After a barrage of tests and a review of a senior cardiologist I've been released. Isosorbide has been increased from 10mg to 60mg daily. They'll be pushing for a review with my Cardiologist asap. Was already down for that anyway after last week's episode.
Glad I did call 111 now. Whilst it meant a trip to hospital and much waiting around at least I was fairly comfortable and they did loads of tests so not being dismissed as anxiety/panic. I asked what I should do if i get further pain. Was basically told every new event needs to be investigated in full. Lesson taken onboard.
Thank you to everyone that responded to my earlier post, meant a lot.