My 1998 octavia has been fantastic in the many years I've had it (from new pratically)220k miles trouble free. This week though it's started to over heat. Seemingly I can't do more than 10 miles with out the temp gauge reaching the red and the warning buzzer sounding. It only takes a minute or 3 for the temp to return to about normal.

I think I read on here once that a similar problem happens when the DMS flywheel wears out? Or what else could I be lokking for?

Nothing to do with the DMF.

You have a problem with the cooling system. Check the coolant level, check for flow, check the oil & oil filler cap for creamy mayonnaise, if you have mayonnaise build up the head gasket has gone.

To check for flow take the header tank cap off, pull the small pipe on the coolant header tank off & hold it over the open header tank. With the engine running the coolant should be flowing out of the small pipe. If it isn't your water pump impellor has broken. If you have a good flow & no obvious leaks, then next thing would be getting a block dye test done to see if the head gasket has blown.

The other thing you could check, is with the engine at idle slowly remove the header tank cap & look to see if there is bubbling in the header tank if there is you probably have a blown head gasket.

The symptoms you describe are classic head gasket or water pump failure.