It does depend on your budget regarding other saws
If you want a track saw, ie a correct plunge saw and track then expect to pay £150 upwards. These will be corded jobbies.
If you want a cordless, then festool do one, which isn't too bad as you can double up on batteries with the tool depending on the job. Expect to pay £1000+ for a saw, track and at least 4 batteries ( they are doing a deal at the moment where you get a free battery ). Having owned one for some time, it wasn't worth the extra cost to have cordless, but some situations it did help, but wasn't a game changer.
Remember a circular saw like you have listed is completely different to a plunge saw which does sound like where you want to be. A plunge saw is quicker, neater and a damn site easier to work with than a circular saw. The track doesn't require clamping, just drop it on the timber and away you go. I've not used a circualr saw in 4 years since owning plunge saws.
All my tools are Bosch now and i can say the Bosch plunge saw is great, but Screwfix do their own brand of plunge saws fairly cheap and they do the same job as any other more expensive tool.
It only comes with a 700mm track but you can buy extra ones should you need them.
Once you have a plunge saw, you probably will never use a circular saw again