I have found this interesting site https://wizdom.ai/dashboards/leave-or-remain-impact-on-uk-research about EU funding for research and how this impacts universities and regions.
It shows that Britain received the second most significant funding as a country (only Germany received more). EU grants were most significant for the universities of Oxford and Cambridge. According to these figures, the Open University received well less than a tenth of the amount these universities received but the amount is still large (26.8 million) and presumably supported a great deal of research work. This, of course, feeds back into the production of teaching materials and informs teaching more generally so this will have been significant for the quality of courses (as with the other universities).