Thanks for your reply.
Yes I have set the Mac to sync with iCloud (I think - I went to preferences in photos. On the iCloud tab, iCloud photos is ticked, download originals to this Mac is ticked and shared albums is ticked. I have also checked in settings on
the Mac, in internet accounts, photos is ticked. I tried unticking and re-ticking this box in case that helped it it didn’t.)
there are over 9000 photos so they are not all from photo stream - I suppose it is possible the new ones are coming in through photo stream?
Before posting this question I have been scouring the internet to find a solution to this issue and someone said to make sure photostream is on so I actually just turned it on in my phone, it wasn’t on before.
In iCloud.com there are 9246 photos, on the MacBook there are 9532.
I have just looked at the Mac now and it says ‘uploading 9356 items!! I’m really worried the MacBook will put the deleted photos back in iCloud, not sure if I should pause it or let it do it’s thing...it’s been doing nothing all day, not sure if this ‘upload’ is because I turned photostream on or maybe I changed something else...