I traded in a Mk 3 Jazz for an ex-demonstrator HR-V (1.5 CVT) just over 3 years ago. Aside from the temperamental auto idle stop (which the Mk 3 Jazz also had) the vehicle has been well-behaved and provides a very pleasant driving experience. The HR-V's reputation was tarnished by bugs with the early production (from Mexico but shifted to Japan about a year ago) and sales were hampered by Honda setting the pricing a bit high (which didn't affect initial sales as supply was the constraint but set a bad precedent). I think the diesels were a bit more buggy than the petrol versions. There's a lot of discussion at
https://www.hrvforums.co.uk/index.php but it has gone much quieter in the last couple of years which suggests that most of the bugs have been resolved.
The 1.5 litre engine has proved to be very economical (average 50mpg) for my usage pattern (mainly A road 50-60mph cruising) with no hint of the Atkinson cycle which made the Mk 3 Jazz less pleasant to drive.
The HR-V's boot is definitely a size bigger than the Jazz and I don't think you'll find any other vehicle of the same size with as much internal space. If you forego a spare wheel then you've a bit more space under the boot floor. The HR-V's rear seat headroom is reduced on the EX version with the sun roof. I've got the SE and the rear passengers have plenty of room.
For pricing take a look at the Honda approved used vehicle stock
https://usedcars.honda.co.uk/en/honda/hr-v . Vehicles with registration numbers beginning with 'O' are probably ex factory stafflease vehicles and, I would hope, be well maintained and de-bugged.