I designed a site http://www.castlecottagebandb.co.uk and used Lightbox v2 for showing the images and was all working fine till a few days ago.
The family member i designed it for says the images are not opening up with the nice way Lightbox does, it just opens a new page just with the image in it.
I don't get this on my computer.

How can i sort this?
And if anyone has time could they check if it loads right for them?

Works fine for me. Maybe they have Javascript disabled? When I do that, it does exactly what you describe is happening to them.

Got them to try that but they saying it's still not working.

Try what? Turning on Javascript?

Yeah got them to turn it on.

Now have them clear their cache and try again. It's a very simple script, it should work, unless their browser is ancient.