You might be interested that Maplin also do a laptop power converter that
runs from 12v. I've got one when they were on offer, and it's great. I
think it was N11BB from the maplin site, but it was on offer at £20.

Just remembered that I already have an in-flight laptop inverter that
would do the job - do you (or anyone lese) happen to know what voltage
they use for power on planes ? If its 12v I'm all set ...

Regards,

Andrew