Phil,
Before you add steps to your mast & all the potential problems they may introduce such as extra windage, extra weight aloft, corrosion problems at fixings & snagging halyards....can i suggest you make up a 4 point strop, with 2 long lengths you step onto, another connects to your harness & the 4th point to a shackle or similar at top of mast, you may be able to take the strop with you when you go up, then hook it up when you get there, then simply stand up in to it, adding a short length of line between the two foot loops, in front of the mast, will help stepping into it & help to keep balance, worth a try??
If you go for the steps, the TH next to your mooring has a good set-up, where the outside points of each step are "tied" together with a vertical line, helps prevent snagging halyards.
cheers
shaun