Thanks Early Riser, I will probably be going on carer's leave soon and when that finishes I may not be in a position to return to work.
Career breaks or anything else that is at the discretion of the employer seem to be non runners in my workplace.
For some reason, I thought that single scheme service would be amalgamated with previous (final salary) service and a calculation done which would have a negative effect on the final salary service. It's good that this apparently isn't the case.
You are correct of course that it is preferable to stay in a final salary scheme and keep accruing service in it as once you leave for more than 26 weeks, that is that in terms of accruing more final salary service.
Another scenario that I've been thinking about is - someone in a final salary scheme leaves for a lower paid job, what is the effect on their pension and lump sum. From what I've heard, final salary pension calculations are based on the "average of the best 3 years in the final 10 years of service". If this is the case, taking a lower paid job might or might not affect the calculation. If someone intended to take a lower paid job it might be preferable to preserve the benefit from their previous job, wait 26 weeks and be in the single scheme for the new job? I haven't given that much thought to it though.