I did their kickstarter and they sent me a couple extra heads. The threads are "standard" according to them. If you want a set, it would probably work with one of your handles.
Cool! I'll send you a PM later.
I started shaving with a safety razor two years ago and I dont have plans to use the cartridge razors again.
Moving to safety razor was easy, took me couple of shavings to figure it out, not cuts so far. I am using a Merkur 34 C, my favorite blades: Feather, Astra, Guillete silver blue and PolSilver, shaving soap: Tabac or Dr Harris.
DR Harris makes my absolute favorite creams, mass-produced or otherwise. Truly fantastic stuff! I would recommend it to everyone.
I'm not a big fan of their soaps, but I love the fact that they are one of the last of the 100+ year old British houses to still produce a good tallow-based formula. Geo F. Trumper, Taylor of Old Bond Street, and a few others, have reformulated their soaps into crap over the past 5 years or so, but DR Harris still makes a good, easy to lather soap.
As a side note, the fragrances that DR Harris offers vary a bit, depending on which product you buy. In particular, their almond cream is of the "sweet marzipan" variety, whereas their almond soap has a dry almond flower scent. Likewise, Marlborough cream is quite a bit warmer and less smokey than Marlborough soap and aftershave. To my nose, Windsor cream, soap, and aftershave all pretty much smell the same, but with different intensities.