If you’ve got a 1.4 petrol, get a compression test carried out to see if you’ve got any compression leakage via the piston rings. If the compression rings are worn I’d expect the oil-control rings to also be worn. I assume your not noticing lost of smoke from the exhaust when driving?
Also, drive at a constant 60mph on a dual carriageway for a couple minutes, take your foot off the gas until your speed drops to 40mph (but don’t use the brake to slow the car down), and then floor it (all in top gear – so don’t change down). Look in the rear view mirror, if you notice smoke when you floor it, you probably have worn valve stems, guides or valve stem oil seals.
If the above shows no noticeable signs of oil burning, it must be leaking, so when it’s not raining, pull the undertray off and check the underside of the car carefully to see where the leak is. I would top up with oil immediately after removing the undertray (if it needs it), so you’ll also be able to see if it’s leaking from the filler pipework.
Cheers
Jeff