Opened the bonnet, looked to LHS beyond screen-wash reservoir, removed cap on (?) hydraulic oil, found it to be RED in colour and below minimum level when engine not running.
Went to shop: insisted I buy hydraulic oil for manual - GREENish in colour! Panicked. Went to another shop: bought hydraulic oil for automatic - RED in colour.
Confused!
Can I mix manual and automatic hydraulic oil?
Low/dry reservoir - does it greatly damage clutch?
It sounds like you opened the power steering reservoir. If so, these usually use the same red dexron fluid as automatic transmissions.
Usually there is a symbol on the cap to identify it. Quite often the power steering has a steering wheel symbol. You really need to know exactly what to put in before you add anything.
Look in the owners manual (if you don't have it, check online there may be a PDF version available). That should both tell you what the various reservoirs are for and what is supposed to go in them.