@jamiejones85 

OK so about 110 sq m with cavity wall insulation a good level of loft insulation, double glazing but uninsulated floors.  'Feels' like 3-5kW or less.  My house, 7kW, needed 3100 kWh to heat it month to date (thats to house not from grid), yours is 1274kWh, suggesting yours is 2.8kW.

So I think we know your house loss is ~3-5kW probably towards the low end of that range.  So you are likely looking at say a 5kW heat pump (there arent many that are actually less and you probably want this for DHW) and 2kW or thereabouts per floor.  You may well need a volumiser to keep system volume up to reduce short cycling.

As to emitters, given the geometry you could possibly consider a single A2A on the landing, if you leave the bedroom doors open, plus something in the bathroom.  However it might be difficult to manage/unsatisfactory and, if it were my house I would want to speak to someone first who has actually tried this arrangement before departing from A2W.  Its just possible you wont need heating upstairs at all if you dont mind it fairly cool, but you have said you need cooling upstairs so something has to go there.  You could possibly run the experiment with no upstairs heating in your current setup, see how the rooms settle.

Downstairs I cant see A2A being a good fit, its just too segmented, although you might just possibly consider A2A in the 4 main rooms.  But it lends itself to A2W.  Conservatory a possible problem space depending on solar gain/insulation/shading.

I would say there is at least a reasonable chance that microbore would work.  In principle you can get 750W through microbore at 0.9m/s and DT5 which may be enough for every room.  It will depend on individual room calculations and plumbing geometry however and needs to be worked out properly.

Cooling - if you go A2A obvious, if A2W perhaps fancoils in living room and landing, although the microbore feeds may limit effect so if you could do a couple more that would be good.  No guarantee this will work well enough and certainly it wont be full aircon, just some light relief.  Is closing blinds/curtains on the south side an option?

Im sure others will have ideas.  Id probably do the calcs, see if I can get away with microbore and if so just upgrade rads, if not think more carefully about A2A, but this is just a gut reaction not one borne out of any experience except my own house and a couple of community centres (in which I did A2A - but these were a small number of large spaces).

Hope that helps at least a bit.

Thanks, I'm thinking the same, I cannot make A2A work unfortunately without open plan downstairs.

The microbore is either blocked or the system really unbalanced, some rads barely get warm.

I should get someone round to a proper look but now the warm homes low/no interest loans have been announced that makes me want to wait until the details are fleshed out on that. I can at least start looking into local heat geeks.