ASHP worth it or better to upgrade the boiler?

[howdoyousaynejc]

Not an expert at all here, so please bear with me.

We bought a Victorian terraced house early 2 years ago that was maintained quite well, with a heating system consisting of UFH on the bottom floor with its own manifold and each room being a zone. We also have 5 radiators (2 aluminium cast) upstairs with only 1 thermostat in the hallway, with 2 cold water storage tanks in the attic and a hot water cylinder, all hooked up to a Drayton controller.
The boiler is a Logic System 18 boiler.

Parts of the heating system were quite old, so during our survey we had to replace them:

• Replaced the hot water cylinder with an unvented Megaflo one and disconnected the 2 cold water storage tanks
• The UFH pump gave up after a week, but turns out it was failing for some time already and caused a pressure build up in the system causing for the boiler to start to kettle and being above 3 bar - I'm assuming the boiler pump was overcompensating for the failing UFH pump
• I'm assuming the boiler is 10+ years old and the previous owners haven't had it serviced for a few years, as we didn't find any documentation on it, so we had it fully serviced and the cleaned a bunch of gunk from it and over a week or so it completely stopped kettling

So now we've built up our sink-fund back up to a point where we're considering improvements to the house again and one of them is obviously our heating, here's what we are considering and would love advice on:

• Our roof is V shaped with only half of the attic insulated, so that's the first and easiest thing to do (we haven't done it so far, as the empty Cold Water Tanks were too heavy and one them even leaking slowly, so we have to replace the whole plaster ceiling)

After which we then have multiple options:

1. Install a ASHP and let it run over the current system (UFH downstairs + radiators upstairs) and upgrade to an UFH upstairs in a couple of years?
2. Wait a couple of years and install ASHP together with the UFH upstairs
3. Wait a couple of years, upgrade the boiler and install ASHP together with the UFH upstairs once the tech gets even better

Any thoughts are appreciated

 

[ShaunCorbs]

Is it fully decorated? / can you get at the mains pipework?