Further to this I have found a LR backups folder worth about 6gb Ive just done a backup and deleted all previous backups in the folder, this has worked a treat. So im guessing what I've been trying to delete are the original files (worth 90gb) approx 10k of images in LR. So if thats correct please pretend you never read this post and I'll crawl back under my rock.
Lightroom backups contain only the catalog.
The catalog does not contain your images, it just references the images by drive+path+filename.
Deleting the old backups should be fine; just delete only the ZIP files in the "backup" folder tree.
Ideally your backups should be saved to a different drive than your main catalog so that if one drive fails you don't lose both sets of files.
Your images also need to be backed up to a separate drive. You need to do this outside of Lightroom.
Cheers mate, my warped thinking was that the back up was the original files so when deleting them thats where my problem was. Think I've got it in my numb skull now. Also I've got catalogue backups on external HD and i-cloud, but.........I now need to back up the 90gb of originals....Thanks for your reply.