Dash Light Problems revisited

Hi,This is a repost which I hope is ok, basically the lights in the instrument cluster on my 1987 W126 300SE do not seem to work, neither does the light that would normally illuminate the gear lever. The consensus is that whilst the bulbs themselves may have gone, the rheostat is also likely to be defective. The advice given was to pull the cluster using the little hooks/levers either side to access and replace the necessary parts. I got a chance to look at the dash today and I was expecting to see a similar push fit to my 1981 W107 with gaps in the side to put the keys/hooks but instead I am confronted a sloping piece of plexiglass to cut reflected glare and no visible way in. Do I go in from underneath either side of the steering column? This is a UK car which may have confused. Thanks Jim