The heatsinks turned up. They can be ordered directly from Enzotech (www.enzotechnology.com) if you can't source them locally. These are a set of 8 called the BMR-C1 designed for RAM chips on graphics cards. But that means you can do 8 Pi's with the one set :-)
They are 14x14x14mm with the pins/fins arranged in a 5x5 grid. They are made from forged copper which is a better heat conductor than aluminium and they come with thermal tape applied to the base and ready to stick onto the Raspberry Pi SoC.
They also make lots of other sizes in case you want to cool other chips such as the USB chip.
I have now replaced the B+ with one of the Pi2's. The remaining Pi2's have been replaced with Pi3's. I still need to cut holes in the tops of the cases and mount the 40mm fans but that can wait until the weekend. The desk fan can keep them cool for the moment.
Given the speed advantage the Pi3 now has over the Parallella I am thinking of swapping out the Parallella's as well. Unfortunately the Epiphany chip on the Parallella sits idle.
The ARM part of the farm currently consists of:
1 x Pi2
4 x Pi3
2 x Parallella
If anyone wants the old ones I am happy to give them away but you'll need to pay for postage. I still have some of the original B's looking for a new home too.