Alan - It was up 'the grassy knoll' behind the War Memorial so your photo above is correct but the building I remember as the Mechanics Institute was behind what is now the Community Centre (perhaps it was an extension of the CC). I recall an open yard behind the building in the photo and a single height building which was the Institute; so, it formed a sort of L-shape with what's now the CC ... perhaps, both building formed the Inst.
As lads in the mid-1960s we explored Bedders looking for mischief and once got into the old Institute. As it was a sinle storey there was a hole in the roof (the tiles had been removed) so we climbed up and dropped into the place ... It hadjust been abandoned!!! There were full sized snooker tables covered in dust, tables and chairs, a mahogany bar, mirrored shelves, etc. It was if they'd been supping the night before and just left it. Very strange. I recall another poster here some years ago talking about this too.