Rayburn 499K - Summer mode no hot water frustration

[Barn_Living]

Having moved into a house with a Rayburn it's an ongoing battle. Latest is that I thought simply switching from "Heating/Hot Water" to "Hot Water" I would continue to have hot water (heated up at the previous central heating times). Not so much.
- I have a separate wireless Honeywell thermostat for the Central Heating only (I don't understand why not also for heating...)
- Hot water cylinder above all works fine if I dial up the CH thermostat to tropical levels
- Cooker never used (so slider off) - tried on which doesn't help the hot water situation (unless I'm too impatient) but it's not "pumping" any hot water anywhere
- Rayburn boiler dial set to mid way.

I've read plenty of the user literature (which does mention the heating/hot water switch may be "disabled") and subsequently tinkered around with a range of slider settings, but setting to hot water only without heating isn't working. It seems nothing is driving the demand for the hot water so I don't know how the previous owners managed for the last 20 years without using the immersion heater every summer. Seems a bit pointless to have a rayburn.

Many thanks for any guidance,

 

[BoilerBob]

Best of luck getting spares they’ve gone up massively in the last year. Bob

 

[CBW]

I’m not really clued up on these, but do they have a motorised valve at all for hot Water?