discovery 2 handling problems

hi has anyone else encountered tramlining or a tendancy to wander when driven on country lanes or uneven surfaces my d2 td5 has 18" wheels with goodyear 255/55-18 tyres my local landy specalist has recommended changing all 4 tyres to grabber at's however i would appreciate some advice from someone who isn't trying to relieve me of £600 it has only just passed m o t and i have checked suspension and there is no obvious play i am also thinking of converting to coil springs all round and lowering it 2.5" to meet my needs {towing and family transport rather than crossing sahara}

Even tho it has passed an mot, I would be looking at the bushes and anything steering related, I had Goodyear with the same size and it was fine, however I did swap to general at2 when the road tyres wore out ( got a cracking deal for 5 so would have been rude not to) they do sometimes grab the white line and follow the road camber, joys of linked axles but if it is worrying you give it a good going over before parting with your hard earned..Also check your tyre pressures...

hi i did check and replace radius arms on front but interesting about tyres will check that tommorow