Helen electric items are fine, they may just undergo a necessary and routine security test, swab rubbed over the elec cable,swabbed and tested in a machine, routine test called an NSM. If for example someone passed through security and they had lots of elec items, hairdryer, ghd's, cameras, laptop, lots of leads and connections etc etc that would be a prime bag to be tested, under x ray a bag crammed with elec items is so hard to read, so may go through the routine test. I honestly do not think your friend will have any trouble whatsoever with you heated throw. It is a blanket really with just an elec cable worst case scenario is it is searched and the cable undergos this swab test, I would be doubtful if it was even chosen. It does not come under the items disallowed in hand baggage. It is not too heavy and it will fit very easily it the box which measures bag sizes, don't be worried Helen. If need be go onto the Department For Transport website and you will see what is and what is not allowed through security and acceptable in the cabin of an aircraft.
Link added for you to Department for Transport, hope this helps.
Air travel hand baggage rules : Directgov - Travel and transport
If needed your friend can also check it in seperately, the check in girl will weigh it and if it is not over your friends allowance, (may incur a charge as excess, but worth it to get it over to you), you would then take it to the BX check in which is excess and awkward shaped baggage with your boarding pass and it will go through there and be married up with the luggage for your flight, happens all the time. Tell her to wrap it up well with its own luggage label and would save her carrying it. Another option to consider!!! Happens all the time, it is just so it does not get stuck on the conveyor going up to be x rayed hence the outsize baggage section. I put pictures and lots of things through this section many times. Worth it to get with you what you want.
