On-One / Planet X bikes and components

Any thoughts on why one (me) shouldn't get Tempest?
I'm thinking that for now I had enough of buying and selling bikes all the time and want to settle for a good long while on something. Doing some thinking I decided that it should be something gravel-ish — I don't race, I don't do MTB, but I do like my field paths and forest trails. Also I want something titanium because I never ridden Ti — bought Litespeed, but had to leave behind with zero miles logged. Not only that, but Ti is supposed to be for life, and that sounds good to me. So the question is — will Planet X Ti be actually for life or I should be aware of them? My concern is that warranty would be pretty difficult for me, since I'm in EU, not UK.
Options I have in mind are:

• Tempest frameset — relatively cheap, I have good wheels and Force group on hand, the rest are pretty easy to get my hands, and everything is standard, which is very big pro
  
• Tempest Rival/Force — still relatively cheap, I don't have to build it, just assemble. I had to leave all my tools behind as well as all my bikes, so that would be convenient. I'll swap wheels and sell stock one and group I have off to offset some cost
  
• Merlin All-Road Steel frameset or complete bike — cheapest option, standards are standard, modern, blue (like me some blue), good tubes. On the flipside I've heard quite a bit about Merlin's spotty QC and that fork is fugly as sin
  
• Rondo RUUT Ti — ungodly expensive, proprietary front brake adapter, but will be here in two days, easy warranty, variable geo fork, great looking and in-house developed frame
  I'm torn, as you see, so to sum up, here's three of my questions:
  
• Is Planet X titanium bikes any good or are they snapping like twigs?
  
• Are they any other budget-ish Ti options I'm missing? Say, up to €2K for frameset.
  
• If I order frameset from PX and add headset in customization, would they install it or just throw in the box?