Its a couple of years since I did supply but yes, that's about what I was earning (Swansea area).  The other thing you might want to be aware of is that there is not much supply work about.  Most schools tend to use TAs or cover supervisors instead of paying for supply teachers. Sorry to be the voice of doom but it is pretty hard to survive as a supply this way.

Just been to a Cardiff Education Supply Agency and been told that as from October there will be a law stating that teachers employed as temporary will be earning same scale as permanent staff. Great news I think!

Agree with what has been said above. 

Teaching jobs in Wales are extremely hard to come by and there is a huge surplus of qualified teachers so many of them are on supply.

The lucky ones get work through the schools direct and get paid through Local Authority and therefore get paid to scale and can make pension contributions. This only really happens if the school knows you.

Others end up working for agencies some of whom pay as little as £50 a day (so I have heard - though for most it is a little more, perhaps £70 - £90).

I think you will only ever get a rate similar to the one you mentioned if you work through the local authority.

Sorry to give such a glum picture but that is how it is in my experience.

opendoors:

I am an NQT currently on primary supply in Essex earning £135 per day. I have been planning to relocate to Wales but am really shocked to note that supply teacher will earn £70 - £90 only per day [saw this on internet].