Recommended heating system checks for potential buyer

What checks or inspection would be recommended for an oil fired boiler and underfloor heating system (5/6 rooms). The system is at least 10 years old, owners say working fine at present and have had it regularly serviced (including this year) since they've lived there (9 yrs). We will ask to see documentation & service records on our next visit. Its a floor standing boiler, served by external plastic tank. Surveyor commented tank and boiler look to be in satisfactory condition. As potential buyers should we get it checked further? What sort of inspection should we ask for?