one noisy tappet

1.8 54 reg 5 door freelander (Kalahari) had it for 4 years now and oil change every 6000 miles(full service)
and just in the last 3 weeks one tappet is very loud started of after a minute it would go but its getting longer and longer so today it was 20 minutes .
i take it its a head of job. or just leave it. my freelander is only worth £400 .so dont realy wont to spend to much but its a nice clean one.
and your thoughts are .....
j

You could try a flushing oil. Something could be causing a hydraulic lifter to stick - There are flushing oils available or you can dilute regular [ low cost mineral oil] with diesel about 50% solution. Idle the engine in the driveway for about 10 min's. Drain and refill with oil and idle it again. Final drain and refill with your reg' good oil.
I think you can remove a hydraulic lifter with the head in place. Id' which lifter it is, Cam cover off, cam belt off... remove the cam carrier assembly carefully as per w/shop man'. use a magnet to lift the lifter clear, Dismantle / clean or replace - reassemble. If you have to go that far you may want to consider replacing cam belt, tensioner and coolant pump at the same time.

thanks for the reply. belt pullies pump was all done 9 months ago.
but these last 2 days no tapping at all.
if it starts up again will give it a flush many thanks