Despite the Mazda 3 growing in size over the years (and gaining about 100kg depending on the model and specification) the boot size hasn’t improved in the 11 years between the models you’ve asked about.

The 2007 Mazda 3 sedan had a boot measuring 416 litres, while its 2018 opposite number could fit eight litres less with a total of 408 litres. The 2018 hatchback had even less luggage capacity with just 308 litres.

As an aside, when comparing boot sizes, it’s important to know the exact method the manufacturer has used to arrive at the figure in the brochure. There are different methods and they have a huge effect on the outcome. Presumably, Mazda hasn’t changed its measurement method over the years, so the comparison in this case stands.

Transmission Control Module (TCM) faults are not unknown on these early Mazda 3s. Symptoms usually involve erratic shifting, a failure to select gear at all and having the car go into limp-home mode. The good news is that there are companies out there who can repair your existing TCM, which gets you around the need to buy an expensive replacement. By the way, from what I can gather, any replacement TCM should be plug-and-play with no need to have the new module coded to the car’s other systems.

It’s also worth noting that Mazda in the USA issued a Technical Service Bulletin (like a recall but not for a safety issue) for automatic 3s from this era fitted with the 2.3-litre engine. In some cases, the shift solenoid could lose fluid, leading to harsh shifts and shuddering when driving uphill. The fix was a revised solenoid design but the catch was that the unit lived inside the transmission, so to whole gearbox had to be removed and taken apart to replace the part in question.

The guiding range for your car is $5900-$7800, but your mileage is lower than average, and providing it is in good condition and has a good service history you should be able to get a price towards the top end of that range.