Bonnet catch...

[stackmonkey]

Doesn't seem to be working any more; as in, the bonnet won't close properly, and when it does, it won't stay closed for long.

best way to sort this out?

[V8 Animal]

More than likely it's your cable snagging.
You can adjust 4 ways the plate and grease the linkage.
Remove the cable and push and pull the cable in the sleeving if it snags replace.
V8 Animal

[mav 1]

Definitely the cable by the sound of it. I had the same issue and repositioning the 'nut' at the end of the cable sorted it.

New cables can be bought at most of the online TVR parts websites.