Most of my PhD students come through the Warwick DTCs/DTPs, including through the mathematics institute, MathSys, Mathematics CDT and HetSys, see link. A few possibilities exist for applying for a bursary to do a PhD if you have a specific project in mind, eg the Heilbronn Institute and Marie-Curie programmes.
I have postdoc opportunities as my grants turn over, typically advertising every other year. If you would like to work with me, there are a number of fellowship schemes open to early researchers, eg Newton International Fellowships (anticipated deadline March 2023), a Leverhulme Trust Fellowship and Marie-Curie Fellowship (for people outside the UK). Applications to EPSRC, BBSRC are also possible as named PDRAs. Contact me if you are interested and we can discuss suitable proposals.