Push fit isolating valve type

[yottie]

Am wanting to replace basin taps in a 1971 plumbed house. Thought I would fit isolating valves just below the basin while I'm at it. The two pipes are very close to the tiling so would like the easiest way to fit the valves. Can I use plastic push fit type on the old copper pipes.
thanks

 

[AL66]

Push fit is designed for 15mm copper, the change from imperial 1/2" to 15mm was in 1971 - so you might have either, 15mm compression should fit 1/2" OK (might need cleaning thoroughly to reduce the diameter slightly if the olive won't fit over easily).