Cheers Ruud, I hoped you might come up with the answer. I noticed the word "zender" on the control panel and took a guess but couldn't narrow it down any further.

Fantastic site and amazing to see all the original kit and still in fairly good condition, though it looks like damp is starting to affect the floor and ceiling tiles, so won't be too long before the inevitable decay sets in.

621 a nice clear channel, 540 not so .. but either could have been put to use with some of this equipment as a lower power "community of interest" style station, run in a similar fashion to 648, rather than see it all go to waste.