Can I change from a system boiler to a combi boiler in Glasgow?

Often yes, but the conversion should be based on hot-water demand and incoming water performance rather than simply removing the cylinder to save space. A combi produces hot water on demand, so the incoming mains flow and pressure need to support the outlets you expect to use.

Converting also changes the pipework and may involve removing or disconnecting the hot-water cylinder and associated controls. In a Glasgow flat where space is limited and hot-water demand is modest, the conversion can be attractive. In a larger home with several bathrooms used at the same time, retaining stored hot water may provide better performance.

Doherty's Glasgow boiler service covers combi, system and regular boiler options. A survey should confirm whether conversion is technically sensible before the cylinder is removed.