OK, based in Europe Flying on BA is my main source of SCs!
Just a few hints: Get Flights on BA that are over 600 Miles! So NOT LHR to MUC/BER/HAM!
Things that work are: MAD, BCN, NCE, VIE, CPH or OSL, LIS, ATH
Start your MR not from the UK to avoid the luxury tax!
Cheap Business-Class Fares need a saturday night. So you may do some nice weekend Trips with that.
There are quite interesting through fares in Business Class. So MUC-LHR-MAD yields 200 SCs in Business Class and can be booked for around 700 Euros.
Be careful:
Only oneways or simple returns can be upgraded. So no Open Jaw tickets!
Just book the cheapes Eco Ticket. An Upgrade should be around 70-90 Euro! With that, you can build same day returns, but there is the risk that you cannot upgrade the ticket.
There were some nice fares on MAD-FRA with LA in Business Class. You may have a look if they are still around (Yield 60SC per Segment).
Other Airlines:
Nope, no such deals! Sadly MALEV went under.
AB has no Business Class.
Others have very high prices.
Be aware that only tickets in Y yield for full Economy SCs - which is usually very very expensive. So trips with AB can be very cheap (100 Euro per return) but they only yield 10 SCs per return).