My mini is blowing a fair bit of smoke, especailly on startup and when you rev it a bit.The plugs are tending to foul with oil so I'm assuming its an oil burning smoke. Compression is between 170 & 185 over the 4 cylinders.
Am I more likely to be looking at a problem with the rings or with the head ?

Could be either really.
If only on startup and it goes away, except at bottom of hills- think valve stem seals.
If it does it under load, it's the rings...

I don't believe in re-ringing Minis- if they are worn out and pumping oil, the bore is worn oval/tapered too. There is so much work stripping and reassembling it, I think it's false economy not to bore & hone it, and fit the next size up pistons and rings.
Good oversize pistons are cheap as chips these days. And a 4 cylinder rebore & hone is $100-$150.

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.

just dont start it where people are eating...it could cost you a big fine

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the mokeman cometh...........

It doesn't go away entirely, its just particularly bad when first starting and if you give it a bit of a burst.
Valve stem seals were replace a couple of months ago with the Vitron type.I didn't really check the guides and stems for wear at the time.
All 4 plugs are fouling but number 2 is a bit worse than the others.It does have the lowest compression of the 4 but I didn't think the figures were too bad.