Anyone know what size they are, I've got a couple that look decidedly second hand and need replacing

The Zetec silvertops use M8 flanged bolts with 10mm hexagons rather than the 13mm ones on standard bolts.

This is a 1.8 blacktop and they're definitely smaller than M8, haven't got any M6s in the garage to try but I get a feeling they could be smaller than that

As above, my blackie was M8 with 10mm flanged heads, thats the ally bit to the engine. I think the tin to ally screws are M6 with 8mm heads.

If you'd posted this last week I could have sent you a set, binned a load of old stuff over the holiday weekend.....

Sorry, should have made it plain, what I was on about it is the bottom part of the sump (the bit with the drain plug), so M6 sounds about right