Overhaul? Lead flakes in oil - interpretation please

I have a 1972 Cessna 172 with a Lycoming 0-320-E2D engine and it runs
beautifully. It is on UK private category.
The engine is "original" and total time is about 2800 hours.
The engine had a thorough top overhaul quite a few years ago, maybe
around 1500 hours (new pistons etc) and has no problems with
compression, oil consumption, vibration or indeed anything at all. It
is well looked after.
Now the but.....
At its last annual (Christmas) some metal particles were found in the
oil filter.
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The lab report says:
Filter section weight 397 milligrams
Major: - lead flakes measuring 0.1mm across
Minor: - blank
Traces: - Aluminium alloys - corroded fragments measuring up to 1.6 x
0.5mm
Iron - 0.5%
Nickel - 0.5%
Chromium steel such as sae8617,8620 or 8740 flakes measuring up to
0.9mm across
Iron - A low alloy carbon steel with no significant alloying
constituents such as sae 1010 slivers measuring up to 0.9 x 0.3mm
Miscellaneous - mainly fine particles.
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I think it now means a complete overhaul to zero time.
The choice seems to be:
a) Factory Zero timed engine
b) Factory overhauled engine
c) Have my own engine worked on

What are your views about which way to go with this?

It is awfully tempting to keep the plane running and cut open the new
oil filter at, say, 20hours and see if there are any more particles.
As I said, compressions, oil pressure, power etc. are all good.

Maybe my greatest fear is that if I keep it flying, there may be
damage caused to the crankshaft or something which causes a big price
increase at overhaul due to the part being rejected.

Any advice / comments greatly appreciated.

Les