Ground source heat pump

[Luminous]

I'd like some advice on the best way to provide the supply for the above.

Back story is i'm rewiring a fairly large farmhouse, the original quote just included for 'boiler', immersion and under floor heating. However the ground source arrived today and i'm like "hello! what's this?".
The customer will stump up what ever is needed, but likewise I don't want to go over the top.
The specs in the manual are as follows : "5.1kw - 3x2.5mm on a 25a type D breaker".

I've never had to provide one before so here goes - my thinking has been that 25a breakers are rare-ish to start with so I'll up to 32. Now a type d 32a max Zs is 0.36. Unfortunately the house is having a new tncs supply but is not in yet! So not sure of ze.
From ccu to heat pump is 20m clipped direct no thermal etc.

It's looking likely that I'm wiring in 10mm to stand any chance and I'd still have to find a split load who also make 32a type d mcbs to fit. Or would you install it another way, perhaps with different fuse/switch?

Any advice gratefully received.

 

[Des 56]

The one I just finished
10mm sub main off 40 A mcb feeding a local dist board with isolator and 6 ways,this was filled with 6A 16A type B and 25 A type D (Garo 25 Amp Single Pole (Type D) MCB| MeteorElectrical.com) The site sponser supplies them
This board then fed the isolation and fused switches locally all wiring surface mounted in trunking

You will need to provide for 2 No immersion heaters, as well as the Pump and control circuit,ext frost stat. the heat zoning panel etc so the local board will be very handy