How to survive a non 240v hook up site

Certified Locations are terrific but I find that many in the 'right' place do not have 240v hook up and can be expensive for the privilege. So how do I stretch my leisure battery to last the week?

Many of my 'luxuries' have charging facility but mostly only on 240v.

Laptop; MP3 player; Torch (big one); Camera battery charger; mobile phone; rechargeable toothbrush; etc.

Firstly I have needed to replace my 8 year old ailing battery and chose a 115 Amp from Halfords - £89. Seems fair value.

Secondly I have bought a Power Inverter. This is plugged into the cigarette socket in my car and converts the 12v to 240v with a normal household 3 pin socket built in. These have to used with some care and the 300W version I have purchased  will not boil a kettle!  But it will allow you to plug in one or more of the various items needing a 3 pin socket for charging. Every time you drive the car - it will charge.

I chose a 300W 'Bestek' from Amazon at some £25 and I think it will do the job. This model also has two usb ports which accommodate a couple of my items capable of recharge by this socket.

Any other ideas for a non 240 site?  I already carry candles for evening light  and solar panels only provide 12v battery recharge.