After 168k miles the flywheel is grumbling disconcertingly at around 1500rpm on 4th, it round like something has broken off and is rattling around - ok at other revs though, and no hint of clutch slip which is weird. 

 

Question is, the old girl is coming is 15 years old, she's probably not worth £1k on the market but worth more to me. She's looking a bit saggy, wheel arches, doors and rear suspension arms have tin worm, so do I replace with a new DMF or convert to single mass?

 

 

The DMF function is effectively in series with the clutch, so DMF wear/malfunction won't necessarily be accompanied by clutch slip. The DMF reduces harshness and vibration which you and your passengers will appreciate.  However, it also protects the gearbox from torque peaks, which may have allowed the designers to make the box smaller and lighter than it would otherwise have to be.  Only you can decide on the cost v benefit equation, but I suspect unless its a DIY job that the labour cost will comfortably outweigh that of the parts. Is a solid flywheel much cheaper than a DMF ?