[woodcote]

It's a tight space... but it's a space for a track

The 800mm width is too narrow for a full 180-degrees of standard Radius 2 corners with borders (I measured that at 865mm) - so you'd need a R1 in there, but that gives you the chance to use an R3 piece leading in (or exiting) for an interesting complex curve. The longest straight is going to be about three (maybe almost four) feet long, so the circuit would be all about testing low-speed handling. If there is the potential to add more to the right-hand leg (a temporary board, maybe) that would give you a little more straight - my old tiny test track had a six foot straight, which was just enough for a blip of full power to test acceleration and braking. That had a 180-degree R2 turn at one end and a R1 hairpin at the other.

I did sketch out a version of your plan in Tracker2000, including the Scalextric Sport barriers, a bridge rather than the crossroad piece, a single crossover (to use both lanes), minimising R1s and including five R3s...

   

Plus another one that maximises the straight length, has no bridge / crossroad and includes four R1s and mostly R2s (only one R3)...

   

That one runs best anti-clockwise - accelerate out of the tight hairpin and brake into the R2 left-hander.

A lot of the design (especially with bridges and elevation) depends on how you can access the tables - what edges are up against a wall etc.