Do I have to amalgamate my pension if I rejoin public sector

Career breaks or anything else that is at the discretion of the employer seem to be non runners in my workplace.

That is a real pity. Worth a try, all the same?

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.

Not sure, but I don't think it is quite like that. The average of "the 3 best years in the last 10" relates to pensionble allowances rather than pensionable salary, which is the average of the final 3 years (AFAIK).

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.

No, you are ok on this score. You keep the pension terms and conditions for your existing scheme for the years that you have served. The Single Scheme terms would only apply to service in a new job at a later date.
 
This is still niggling at me. I am afraid to stick my head above the parapet just yet as I suspect I might have the abatement issue. Fore warned is fore armed, I don't want to be unreasonable just want to fight my corner so to speak. By my logic I accrued a defined benefit pension over approx 15 years in admin in the University sector. That pension is preserved until 60. I do not have the option to leave it to accrue any growth in benefits. It has to be drawn down.
After a couple of other jobs I subsequently took up a public service job in a primary school where I have been since 2009. If I effectively loose my DB pension from 60-65 due to abatement will I be credited the five years of pension to my current role? Those years should not just disappear from the count of years service. All advice appreciated
 
After a couple of other jobs I subsequently took up a public service job in a primary school where I have been since 2009.

I think you are in the clear because you took up your current role in 2009. Abatement, as it is currently applied across the public service, only came into effect on 1st December, 2012, and it was not applied retrospectively. You were already in your second post at that time. So you should be able to claim your university pension at 60 and continue working as normal in your current role.

Abatement prior to December 2012 applied to people being re-employed in their former department, often effectively in the same job, and collecting both a salary and a pension for the role. It did not apply to people leaving one sector in the public service and taking up a different role in another sector.
 
This is from the Dept of Public Expenditure and Reform, referring to the 2012 Act. It should allay your concerns about abatement, given you were in your current post since 2009:

6. Extension of pension abatement: The Act enables the extension of pension abatement so that a retiree’s public service pension is liable to abatement on re-entering public service employment, even where the new employment is in a different area of the public service.This extension of abatement will come into effect when the Minister for Public Expenditure and Reform signs a commencement order. The change will apply in those cases where a person with a public service pension in payment takes up a public service post from the date of the commencement; a person in public service employment on the date the order is made will not be affected by the change while he or she remains in that employment. (See section 52, excluding subsections (6) and (7), of the Act.)