You could incorporate some soil conditioning compost while your'e digging, but it seems a bit of a waste of resources if you're only going to turf it. When you've prepared the area properly and are ready to lay turf, throw Growmore all over the areat till it looks like fallen blossom, give it a rake over and then lay the turf.

You say it's 'sandy clay' which could be well draining if the 'sand' predominates or not, if the clay does! If you tip some water on it, does it drain quickly away or stay on the surface? If the drainage is poor, I would say that is as important to put that right as adding the nutrients and soil conditioning. That would mean spiking or loosening the soil as deeply as you can.

i.m.o..........take it or leave it dont re-turf it plant it! ...i did the same 2 years ago took up the weed infested 40 year old turf stacked around the back put carpet over it to exclude the light to rot down added 50 bags of manure type stuff dug over my solid clay let the frost break it up over the winter dug it over again added a bucket of blood fish bone pellets planted it ok i had some help with plants as my mum was leaving her house so i got hold of some good establised hydrangers rhododenruns ect ect...that was in feb lasts year it still looked empty so sowed loads and loads of annual seeds by may/ june that garden was unbelivable!! people kept stopping to look at the whole garden was a riot of colour if u want me to show you the pics before and after just pm me....