Charge function just came on and can't turn it off

Hi guys I really hope someone can help, I unplugged the car today and travelled about 1/2 a mile and after a couple 100 meters down the road I pressed the windscreen wash and as it did its 3 squirts I heard what sounded like a relay click down my the glove box now I confess that normally I have my music on loud so this might be nothing.
So I arrived at my destination (1/2mile) turned the car off, got out opened the boot, a couple of minutes at most closed the boot got in the car and started the car, and I heard the engine rev and thought what the ####, looked and the charge function was on, thought I must have knocked but NO the charge function won't turn off can't change to save, turned off and back on same, drove back home and parked, opened boot closed restarted still on charge mode??????? I also have a message which says "engine started to maintain fuel system"
Now I know I've dropped a big boo boo because the service was due in February and as the dealership didn't contact me I was going to get it done at a garage and kept putting off.
I've noticed that some people are referencing something to do with 3 months fuel etc but I'm pretty sure my fuel isn't that old I terrified to use the car because not only does it use twice the amount of fuel but I'm scared it might damage the drive battery.
PLEASE HELP ME
On a separate and completely unrelated matter how well should the progressive breaking put charge back into the battery because I swear mines not been working correctly from a very short time after driving from the forecourt but the dealership keep fobbing me off

Don't panic.
You need to add a minimum of 15 Litres of petrol/gas.
The car thinks the fuel is starting to get stale as non has been added for 90 days and so will run the engine to turn this into electricity for the traction battery.
The PHEV is a stupidly intelligent car!

SurealUnReal said:

On a separate and completely unrelated matter how well should the progressive breaking put charge back into the battery because I swear mines not been working correctly from a very short time after driving from the forecourt but the dealership keep fobbing me off

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You will get a bit of charge back from regenerative braking, but not really very in town driving where you're only braking for seconds at a time. Where you get most is when it's working like engine braking descending hills - ie for minutes at a time. You could think of regen braking more as a way of reducing the wear on the brake pads by using the motors as generators to provide resistance - it's a braking function, not really a charging function.