You can find past papers and information about the TMUA at the official website here. I have produced videos going through the 2019 papers and put them into a playlist here (to be completed October 2020!)

TMUA 2019 – Playlist of Paper 1 and Paper 2 solutions

If you are preparing for TMUA you might also find my MAT videos useful – the syllabus is similar and the short answer questions from the MAT are particularly good practice for the TMUA too.