Balancing auctions are pay-as-bid, the alternative is lights-off.

Capacity auctions are iirc pay as clear. Maybe day ahead as well.

One thing to consider as well is that without some external stimulus scheme all of the fossil/nuclear (even ignoring CFD schemes) would immediately go bust IIRC if the market was solely pay-as-bid because wind and solar are cheap but extremely spotty so the price would either be 0 or 1000, probably not the latter long enough to keep the gas plants we currently rely on in business => no more power on cold calm nights.