Just so you know. Right click on pic, click 'Copy image location' then click the little box next to smiley where you post on here, paste in link, ok, &...
It does look as if hitch could do with some lubrication. Get an aersol can of grease or WD40 will do if thats all you have & give it a good spray & it might be ok. Use a large screwdriver or nail bar to prise back tab under hitch bal while lifting handle.
Cheers for the info on how to post pics, I've struggled a few times before! - I was going to the tab that said "get url to share photo with anyone" and pasting that in, no idea why that doesn't work, but at least now I know another way!
He has tried with a screwdriver, but I'm taking down a larger selection of suitable tools tomorrow. Also going to see what this other parts place says about it being the wrong hitch/see if they have one. If not, the chunky one it will be!
personally i would go with not enough lubrication ,its very uncommon for a hitch to lock up at all .if its free from the car spray inside present hitch with a good quality lubricating oil (not wd 40 which is only a water dispersant) then apply grease internally to the hitch ,also get hubby to rub the tow ball down with emery paper then wire wool to ensure theres no rust spots then grease ball thoroughly .cheaper than a new hitch and you would have to grease a new one anyway
Just an update to say that when I got there, I realised there is a part missing - there used to be a sort of "trigger" in that cutout slot on the lower shaft of the handle - it wouldn't come off on the flat either, so think this must be part of the problem. We are now back (after a brilliant festival!)so may be back for some more advice if we can't resolve/replace easily ourselves. Thanks again all!