How often do you climb the mast?

[cliff]

<snip> I can get a rigger to change my tri-colour bulb for £100 but it's going to cost me over £250 in climbing gear to replicate the set up I had at the climbing centre. How often do these bulbs go or the VHF aerial fall off?

Frequently in my experience - usually due to corrosion rather than bulb failure. Having said that I use a couple of mast monkeys when I need the bulb changed / cleaned or other work at the top of the mast.