Aye.. the lad has a "Ti" which I think stands for "Turismo Internazionale".. and not "Turbo Injection". Still it's a light car and 150bhp, so pretty nippy. I guess the seller hasn't had it long (thankfully) if he thinks there's a turbo in there somewhere.
0.5 ltrs per 1000 miles is within known usage for the T/Spark motore. It uses more if you boot it.. but even if you drive like a nun, some engines use oil and some don't. My 145 (nun) uses half a litre between 12,000m services.. but that seems to be very unusual. At least it keeps you interested in what's happening under the bonnet, which is good.
The cam-belt and balancer belt are supposed to be swapped at 36,000 intervals. The kit is about £130 if you can do it yourself.. so £200 as a budget for someone else to do it is a little optimisitic. Good specialists will touch you for £350.
You may want to put a new water pump on there while you're about it... and it could need new plugs. They're the titanum coated jobbies (4 of them at least - the other 4 are twin-electrodes) so you're looking at £60+ for a new set.
Rust isn't a huuuge problem.. the body is mostly galvanised but the floor isn't. You'll have rust at the trailing edge of each footwell... there are half-moon shaped drainage holes where the rubber schutz coating lifts with age and allows corrosion to get a hold.
The floor-to-sills seam*may* also be affected but is usually in better nick and migh just need some underseal or a light clean up and re-seal, rather than a major welding/filler job.
It's worth going to have a look..
The fella could just be getting shot of it because it has quite an expensive amount of work coming up relative to the value.
If the lights on the dash go out (make sure they do come on.. sometimes the bulbs of warning light mysteriously fall out..
) then chances are that it's pretty sound - just look for the usual type of car problems.. clutch, gears, brakes, exhaust etc. not because the '46 has many particular vices other than floorpan and cam-belts can't be scrimped... but it's getting on a bit, after all.