NCA training
I agree with a lot of what has been said already.
I too left a good well paid job in civvy street to go NCA. Do I regret that, NO. Age was no issue - NCA recruits ranged from 18 to 30 on my course. The training was hard but if your fit enough, you won't have a problem. You won't have any dramas from training staff about being 30 and if anything it will aid in your credibility to become a SNCO once you have gone through the NCAITC at cranwell.
As for SAR as NCA, you would first have to get streamed rotary and go through the helo course at shawbury. Once completed, it is very rare as NCA to go SAR from shawbury if you have no previous military experience. As said already, you would probably go SH and spend a couple of tours in the sun and sand before being considered for SAR.
As for leaving a loving relationship, that is something you are going to have to find the answer too yourself unfortunately mate. Service life is hard enough on relationships and thats when your mrs wants to be involved in RAF life !
At the end of the day, I dont regret a minute and love what I am doing now. Its a chance to do something exciting and adventurous with your life and I can't think of any other job I would sooner be doing.
Good luck and get yourself to one of the NCA days at cranwell - all will be explained.