widdowson2008 wrote:Did I understand you correctly? 1/2 litre AFTER a pump change? If so, I'm not sure how they managed that

Who knows?.
Cold levels were at MAX on the forecourt, then expansion tank empty next day at cold. Journey home was only 50 miles.
They reckon all it required was 1/2 litre to get it back up to MAX !. My photos taken on the drive tell a different story.
Fetched it couple of days ago, and the expansion tank down 3-4 inches on cold check.
Their mechanic's response today was same as last time - "top it up, and bring it back. Won't do it any harm".
Talking to legal folk tomorrow, but concerned that rejection won't be possible, or that we'll have to take a replacement. I don't trust them to make a
cup of tea, let alone provide a checked, serviced, prepared vehicle.
They simply don't have the ability/willingness to diagnose problems, nor fix them properly so nothing but full refund will be satisfactory.
They've had two chances to get it right - prior to sale, and on return last week.
Rather than the vehicle having gone 'bad' during ownership, it was not fit for purpose at the point of sale. We've not used it other than fetching it home twice.
If anybody does have experience of rejecting a vehicle, would be good to hear from you !
Thanks too all for your expression of concern, and all advice received to date. Will be happy to name the retailer when I'm free to do so.