Ratemyplacement is good, although it's focused on internships many companies advertising there also have graduate schemes.
Looking on
careers websites of companies you may know of or are well known in your sector, as they may do graduate schemes. E.g. for Aerospace -> Airbus, Boeing, GKN, Rolls Royce, Safran.
Recruitment agencies such as
GRB who help to recruit for graduate schemes. And generic ones like Hays, Robert Walters etc.
Linkedin is very good for job searching.
Targetjobs
Gradcracker (even if you don't do STEM it gives you a good list of companies to look at)
Your careers team at university may have a spreadsheet of companies and their graduate schemes.
Lists such as
https://advice.milkround.com/the-times-top-100-graduate-employers. (Go through the employers see if any interest you)
Indeed, Monster, Milkround etc also good.
I've highlighted in bold my favourites, best of luck!
Do bear in mind the websites such as graduate.jobs and prospects aren't useless it's just that large companies generally recruit graduate schemes from the start of September onwards rather than at this present time.
Do you mind if I ask what exact degree you did?