Nillchill

i used something like this, replaced 2 of them , they seem to do the trick 

Just measure the diameter and make sure you get the right size

https://www.vital-parts.co.uk/round-domed-chair-feet-354-p.asp

Saw this on astro buy and sell

http://www.astrobuysell.com/uk/propview.php?view=80764

But its in Cheltenham, though it may be reasonable courier charge

I have noticed the same with my 150pl , if you look down the tube in daylight , you will be surprised how much light bleed is there. Also I have noticed that the seam at the base of the tube bleeds light into the tube. I have found that a bit of tape on the seam has helped as has the fan plate I have fitted to the base.

Good luck in booking it all

Rest peacefully sir, you have truly earned it. You will be missed by so many. A true inspiration.

In the Starmen TV program the other night, one guy had mounted his pillar onto a platform supported by a couple of scissor Jacks, he would then wind them up to allow up to 24 inches of extra height.

they only cost £18 each

1.5 Tonne Scissor Jack | Screwfix.com

might be an option for you