Hi screwfix do the Scheppach HS105 its £235 maybe cheaper if you shop around. Looks similar to my old Ryobi I started with 20 years ago. the saw lasted many years before I upgraded do to motor failure (no shame it work really hard). Anyway it has a (full length)* locking fence front and rear (it will be solid) and an extending side section to allow for 600mm cutting. However, setting the fence is crucial as it will not lock automatically square to the blade (none of the budget saws do). In my experience it only takes a minute to square it. The mitre gauge will be rubbish but tweakable. zero clearance blade inserts will be easy to make. The riving knife is adjustable for height meaning you can use the saw for rebating or groove cutting (for the likes of a drawer base). Most other saws don't allow for riving knife adjustment like this and as such operators are likely to remove it, a dangerous move for a beginner as it often never gets re fitted.
Everybody will tell you these saws are s#!t, no good, full of frustration, a problem waiting, unsafe, inaccurate, flimsy.......they are correct on the latter but most are likely to have used in the past a much better industrial saw.
I found my saw valuable to me and of great use in making 'stuff' you and your son will too. Just remember it will take a bit longer to set up accurately.
* Full length fence is another debate