I have finaly tracked the whining noise down in the engine bay after thinking the power steer pump was going to pack it in. I dropped the belts off and found the problem was the air conditioning pump pulley bearing was the issue. Are these able to be replaced in the same pulley or do i have to replace the whole pulley and if so whats the best source to go through for it

Compressor clutch bearings are replaceable but can be expensive (cheaper than a new compressor), and its best to machine up the clutch mating surfaces, and adjust the air gap accordingly. there is also a risk of cracking the hub when pressing out the bearing.
You then need to go to a specialist bearing supplier with the part number (or complete bearing).
I have never done a magna a/c clutch before so i cant tell you if there is enough room to do it without reclaiming the gas and removing the whole compressor.
If/when you do get it off you also need to check for signs of the bearing biting into the compressor, if there is then cut your losses and have the compressor replaced.
I checked one of my suppliers websites and they dont list a replacement clutch, only the whole compressor... but thats not the be all end all.

ive had the pulley off today and have the bearing number written down before putting it all back together would be great to replace the bearing which i may be able to do but wanted to know if it was possible or the easier way to go about it

Well bare minimum you need a press to remove the old bearing and fit the new one, and a hammer and punch to re-punch around the bearing. But as i said its best if you can give the hub and clutch plate a light skim on a lathe and adjust the shims for the air gap.