Hi Jacko i have changed all 8 plugs about 1 month ago and all filters and oil it runs ok its just on tick over,
Auto-correct changes Jocko to Jacko on my PC as well.........
You have already done the most obvious thing and replaced all 8 plugs, was this tickover thing happening before you changed the plugs or did it start after.
The first thing I would do is to tip a full bottle of redex injector cleaner in your next tank of petrol, it may just be partly blocked / gummed up injectors. If that does not cure it you may have to give EGR Valve (exhaust gas recirculation valve) a bit of attention, plenty of info on here about it - normally causes more problems than you have but maybe it is only a little bit stuck (it is like having a leak in the inlet tract if it is stuck open at low revs).
Could also be a coil going bad, especially if rear plug gaps have been allowed to get too big in the past and stress the coil insulation - I would suspect rear coils as they run under hotter conditions than the front ones and rear plugs are normally neglected, this forces coils to provide higher and higher voltage than they should to jump the larger plug gap, this can degrade the coil insulation. Check they are all properly plugged in first and then unplug them one at a time (at the dual pin12 volt connector plug on top) and see if vibration gets worse, if it does plug that one back in and see which one does not affect vibration when you unplug it - that will be the one that is not working properly.
A car that has only had little use (50 K in 15 years) may need a good 'shock and awe' dose of redex and a good 'italian tuneup' ,,,,,,,,,,,,,,,,,