I'm thinking of putting in underfloor heating to my lounge (going to be parquet flooring blocks over existing screed) and my kitchen (going to be ceramic tiles over existing screed).
In terms of installation (by the diy-er) and operational cost and efficiency, is the electric mat system better that a plumbed in system?
Always difficult to compare like for like, the electric kit will probably be 10-20% cheaper. In both cases you will probably be modifying an electric circuit so you should use someone who can issue a minor works certificate.
The water based system will need a screed which will be thicker than the one required for electric.