ScottyUK, the high attrition rate in operations is due to a combination of factors including but not limited to, a high unrelenting work load, long hours with high required overtime, stressful control room enviroment, stress due to ongoing testing (written & simulator) required to maintain qualifications & pay, and draconian punitive responses to even honest errors of judgement. The geographic area also sometimes significantly impacts the attrition rate. These factors vary in significance from plant to plant as each plant seems to have its own unique culture formed by a combination of the personalities managing/supervising it, the employees, and its history. I have seen two plants owned by the same utility with significantly different attrition rates. I know of plants that rarely conduct hot license classes because their ops attrition rate is almost zero and I know of other plants that have continuous overlapping hot license and non-license classes because of their never ending struggle to maintain suffcient control room and field staffing. I once left a plant because it was an unpleasant place to work and live. I found and entirley different experience at another plant owned by the same utility.
Before accepting employment you should try to informally talk with those that are already employed. Ask about the attrition rate and the amount of overtime and how much of it is forced. Ask about the work schedule. Some plants work eight hour shifts and some work twelve hour shifts. The twelve hour schedule has the benifit of many more full days off and even provides a full week off every six weeks or so. The downside is that the hours are long and if overtime is regularly required it quickly eats into the available days off. Some people love this schedule some hate it. You have to decide but need to do this before you accept the job. The world of classrooms, examinations, and constant evaulation are just part of the commercial nuclear world and exists everywhere. It never stressed me but I know of many others whos quality of life is adversley effected by the constant worry.
On the positive side, the pay and compensation is excellent. Not only are base salarlies high but there are sometimes significant monetary retention incentives associated with these jobs. I left a position once that included almost a 25% increase above my base salary with license/certification pay and geographical retention bonuses. Some of the retention bonuses are based on successfully passing annual requalification exams. It is not infrequent to see someone loose thousands of Dollars when they fail a written or simulator exam on the first attempt.
I am not at all familiar with the licensing process in the UK. However, in the US, ScottyUK, as a degreed engineer, I would expect you to enter an approximately 18 month or longer program that would license you as a SRO (Senior Reactor Operator) and for you to spend little or no time "on the board" (except during training). I would expect to see someone with both a four year engineering degree and an SRO to be part of the shift supervisory staff. A typical single unit control room has two board operators, two supervisors, and circa five or six non-licensed field operators.
A post TMI requirment is to have a four year degreed and properly trained engineer within ten minutes of the control room. This is called an STA (Shift Technical Adviser). The STA's purpose is to provide an INDEPENDENT (from the operating crew) oversight during accident conditions. I would guess that the UK has a simialr postion and it might be something you might want to consider. In my opinion the best STA's are clearly the full time STA's that have also been through a hot license class. Some plants use full time STA's where other plants make it a collateral position for their staff engineers.
ScottyUK, I hope this gives you some usefull insight and answers your question.