Microbore pipes central heating

This would depend on the condition of the current heating system, if it has been well maintained over the years and you have GOOD circulation to the entire heating system then leave it as it is however micro bore is susceptible to blockage or partial blockage if neglected so carry out some simple tests, check to feel if all radiators get hot when heating system is up to temperature especially the one's on the ground floor furthest away from the boiler/pump. Also check for cold spots at the bottom of all radiators, if there are any this is a good indication the whole heating is in need of cleaning, best method is Power Flushing.

This would depend on the condition of the system whether it as been maintained over the years and as good circulation as microbore pipework is suspectible for blockages. Check your radiators for cold spots on the bottom of the radiators if there is any its possible the system requires cleaning. I.e powerflushing.