Noisy tappet! Is it okay to drive or action required?

Had a noisy tappet for a while, not loud but now sometimes after warming up it gets really loud, not always and it comes and goes in a second so suspect a tappet has died/getting stuck sometimes.
Is it okay to drive lets say 100-200 miles before repair or better not? (will do damage)

Nb: Oil/filter situation good.

Also is there any point in just changing all the tappets without doing much else?

yes should be fine ,you will need to check cam ,and worth looking at underside of rocker shafts

Thanks, not so worried now - sort of

WOW what a result - Trying my best not to make a sale speech but this is near unbelievable
Snaked my way out of this noisy tappet for now, simply cannot believe the improved condition the whole engine is in after my long trail, quite a few products involved but the single one thing there made everything better is Extralube ZX1.

Here's there story and had i known better i would just have added the stuff in the beginning, but at least i have a good feeling that engine is clean now.

Trial start: 1 Noisy tappet, sometimes very sharp & loud (Embarrassing)
Oil/filter 1000 miles old, looking fresh - engine flush - cannot believe the dirty state of oil drained out - new oil/filter with 1 litre of Engine restore - drive 500 miles tappet still noisy but engine getting very smooth otherwise.

Oil looks near new after the 500 miles - engine flush - again cannot believe the state of dirty oil drained out, black in black - new oil/filter, engine runs so smooth but tappet noise still present so now serious about taking it apart, looking to order new tappet set, cam etc. but in desperation added some STP oil additive which helped a bit but not much.

Trolling posts on Landyzone and in the freaking Freelander forum came across some recommending Extralube ZX1, cost 4 times than all the other snake oils for a reason i can tell now, it bloody works, no more tappet noise And this engine haven't run better for years i will bet - like silk - now i can hear all the other things going on.

I wouldn't hesitate putting zx1 in any engine, no-matter what state it just gives so much less friction, will try a little in the diff's and in the fuel tank, maybe a little in the coolant for the pump, not so sure about the transfer box and the automatic gearbox i will stay well clear of.

This is not an add and not affiliated with any products in any way just my experience other may benefit from.

Sure the tappet and cam didn't suddenly repair itself but its got some extra life for now - so chuffed its hard to describe.
Only thing knocking now is me - hard wood

I would not put it in the coolant, the pump bearings are sealed so it would not get near them, personally I would not put it in the transfer box either, it may not be compatable with ATF.