Is there a way of converting a Creo Elements/Direct model into a ProE (.prt) format or other common format? as I am trying to get a quote from a company who are unable to read the PK2 or BD2 format

Hello Tony,

old question, unfortunately the same answer.
Express is a freeware version of Creo Elements Direct Modeling.
You only have the option to save Pk2 Bd2 and export Stl.
All other export possibilities have been removed to prevent the commercial use.

Below you can see the differences

The only "solution" would be to convert the BD2 and/or PK2 (=Modeling Express data) to BDL and/or PKG (=Modeling data)

Once you have the data in Modeling format, you (would) have all converters/conversions available.
However, the "Express to Modeling data conversion" service is no longer officially available - has also been discussed several times in this forum.