Adding new radiator to existing system

dannyjebb

I need to add a new radiator to a room without one.
Luckily the boiler is in the same room, I have attached the radiator and pipework to the boiler cabinet.
Cutting into the CH flow pipe will be no issue but the return piple runs up the brick wall to the boiler with only a few mm space behind it so no room to get a pipe cutter in! I don't really want to attempt to cut it with a hacksaw.
A few years ago we have an external expansion vessel fitted which was fitted with a tee from the CH return. There is then approx 1m of 15mm pipe running to the EV. 
Is it possible to tee into this pipe and run to the new radiator? 
Pipe on the far left is the flow which I can easily cut into. Pipe on the far left is the return, this is too close to the wall to cut into but I could easily cut into the white 15mm pipe going off to the EV on the left?
 Thanks for any advice.

Danny