As the title suggests, when I press the squirter, I get the water on the screen, but I have to manually turn wipers on. Every other car I have had the wipers automatically come on after the squirters have been used, even when wipers are in the off position.

Are you pressing the squirt button for long enough? The wipers should make two passes after a squirt longer than 0.5 seconds.
Can sometimes catch you out. 2008 MY Java Black TDV8 HSE

Problem solved

I wasn't pressing it in long enough! Thanks Paddi

I find this feature quite useful as sometimes it takes a while for the pump to get the fluid out - and the blades have got half way across the screen causing smears. A few very short pushes of the button gets some fluid on the screen before the wipers move.  2012 SDV6 - it's missing a couple of cylinders
2008 TDV8 - it was a labour of love and is much missed