Can't seem to find anything detailed though a search, so wondered if anyone's successfully converted their grille mounted bonnet release mechanism (I have an '85 90), to an in-cab solution?

Can't say I'm particularly comfortable with a bonnet release mechanism that can be opened from outside the vehicle and the thought of fitting a hasp and padlock to the bonnet/wing, doesn't really do it for me.

Interestingly I did the opposite and replaced the cab mounted one with crude front release. The reason for this is no matter how secure I tried to make the cable I could still just reach through the grill and give it a pull to release the bonnet. Both myself and my friend with a TD5 ended up using the reach through method to release the bonnet as it was less effort than walking around the door into the cab every time (very often) we had to lift the bonnet.
The only way to properly secure it would be some form of lock. Even if you replace the plastic grill with a close gaped metal one it can still be easily unscrewed to gain easy access to the release mechanism.

Quite a few different parts required - have a look at the parts book:

Yes, did it to my ex-MOD 90 (MOD vehicles are fitted with behind the grill levers).
Simple to do and all off the shelf parts,

If you pick up a S/H slam-panel then it will have many of them already, then all you need is the leaver / cable and bonnet catch (can't be certain from memory if it is the same but suspect not as I bought a new one). If you keep your old slam panel then you will nee to buy the release mechanism as well along with the plate, a couple of clips, cable nipple etc. Don't forget to use a grommet where the cable passes through the bulkhead, once again can't remember if that comes pre-fitted to the cable.

If you are doing it purely for security then there isn't much in it as a cable operated release can be over-ridden almost as easily as with the lever. I did it because I fitted a Nakatanenga Heritage grill which you can't get your fingers through.

Thanks again for the info guys... you know, as I was hoping to make the engine bay more secure by fitting an in-board release mech - after reading your comments, I think I'll try something else! If it's as easy as mentioned to reach inside the engine bay to access the gubbins, there's little point in me acquiring the parts or spending the time trying to sort it out.

Thanks anyway... top advice and help, as always.