flyingbird,
The AVTECH courses have value, but before making a choice, do a search in PPRUNE for ICAO 7192 D3 Flight Operations Officer course and read up on past efforts to establish one in the UK.
The IATA course will of course be useful to you and recognised by airlines, but the flight operations officer/flight dispatcher training standard as defined in JAROPS and EASA is to ICAO Document 7192 D3. You might look over this link to CAP768
http://www.caa.co.uk/docs/33/CAP%20768.pdf
I am a tad out of date with respect to where EASA are with any formal accreditdation for flight operations officers these days, but you should think about selecting a course with the above in mind.
I have had early sight of the Bristol course materials and was very impressed.