Firstly hello and welcome!

Secondly, I'm afraid I don't really know the answers to your questions as I've not ever worked for the nhs...

But - as far as I'm aware generally secondment positions are basically temporarily working elsewhere - but for the same employer. As such all you conditions of service should remain the same - pension etc. Maternity - I'm sure you would still get it as it's recognised for students so it must be for staff....

I can't see why you would have to pay the salary back - because they are paying for 'work' you've done rather than the promise of work you will do - as it's salary and not a grant or loan or whatever...

For more clarity though I would talk to HR - they are the only ones who will definately know the terms of your secondment if you don't.....

I say go for it - there aren't many of the 18month courses around any more - and if they're still paying you full salary to boot - you can't possible have anything to loose can you???

Good luck with it all - be sure to keep us posted x