Different tyre sizes on same car? Safe or no safe?

Just replaced a 14 inch alloy wheel and tyre on my ford Fiesta MK4 with a wheel from a Peugot 306. Its still a 14inch wheel but the tyre is 175/65/R14 instead of 185/55/R14 that all my other wheels are. I know that different rim sizes can damage the car but the wheel is the same size, just the tyre different. Is this safe to drive or does tyre need replacing to match the other ones (or other side (front. At least.

Also, The new wheel, although same 14inch size is actually a lot bigger and doesn't sit so deep in the screw holes so the wheel is more prominant that the rest. Still plenty of thread and nuts bolted on very tightly but does look a bit odd. Still safe? Any advice appreciated.

That is definitely a safety problem. If I understand you correctly, you have it on the front - two different tyres/wheels on the front is seriously dangerous, and it's also dangerous on the back because it wrecks the roadholding ability (increased tendency to lose control on corners).

If you took that car for an MOT, it would not pass. If you happened to get stopped by the police, they would insist that you did not drive it any further, as you are a danger to other road users.

MOT failure and unroadworthy too.

NOT SAFE! The wheels on the same axle must be identical. The peugeot wheel will have a different offset (the distance from the steering pivot centre to the centre line of the tread. While it may seem ok in the dry, under wet braking or cornering it may well show it isn't ok. Any half way competent MOT guy will probably refuse to even start the test

If this is on the same axle then its crazy and ilgal to boot. All tyres on a car should be the same size. Years ago people used to mix cross ply with radials, there were and still are some crazy people out there.

If one tyre is of a different nominal size or aspect ratio to any other on the same axle it will fail MOT
Anything protruding the wheel arch could be deemed as unsafe