The M3W parts book shows the fuel system parts, available to view on the MTWC website
https://www.mtwc.co.uk/wp-content/uploads/2018/04/M3W-Parts-Book-V5.2.compressed.pdf
Fuel tanks have been known to crack especially around the front mounting bracket, to see a leak here you will need to take the seats and rear panel out. Also fuel sender and fuel pump gaskets have leaked but you would only notice this if the tanks are full.
See also this thread https://www.talkmorgan.com/ubbthreads.php/topics/697614/3

2021 M3W
2013 M3W - Sold
1971 4/4 2 Seater
1934 Sports