My heater is temperamental.
It nolonger heats up quickly. Sometimes in cold weather the heating will just blow cold and some times it will give you heat but nowhere near as hot as before. Skoda wants £400 to book in for a look to give advisories not including replacements. Coolant is normal level but drops the odd time but is always topped up to be just under max. Oil temp is slow at heating up but temp is upto 90 and is always at right level. Any ideas and if known to be simple fix?

The engine light pops and when we scan it shows colent pump A and coolant pump B circuit