Try any of the big extractor fan companies -- they all make whole house systems now. Some offer free design services and the systems are easy to install.

Thank you Dr T. Will make enquiries.

As an introduction it is worth mentioning that we as a company offer all 3 systems - Passive Stack, Central Extract and Heat Recovery - we are therefore able to give (hopefully) an unbiased approach.
 
Passive Stack
- Uses no energy to operate
- Recovers no heat from exhaust air
 
Central Extract Vent
- Use electricity to operate - 1 fan (extract only)
- Recovers no heat from exhaust air
 
Heat Recovery
- Use electricity to operate - 2 fans (supply & extract)
- Recovers a percentage of heat from exhaust air
 
Operational Energy
Operational energy is the energy which is used to operate a dwelling. In order to assess which of the 3 uses least energy to operate, you should process a SAP (Standard Assessment Procedure) calculation for any dwelling which is being designed. SAP will consider how much energy is used and also the impact on the heating demand. If you perform a SAP calculation to include each method you will see the impact of each upon the overall energy use of the dwelling. Passivent offer a web-based SAP calculation service whereby you can carry out such calculations - these are however at a cost from £79 per dwelling dependent upon floor area.
 
Our experience in such comparisons show that it is difficult to predict the difference without carrying out a SAP calculation. However, in general you could expect to see Heat Recovery becoming more energy efficient as the air permeability of the dwelling becomes lower than approximately 5m3/hr/m2@50Pa.
 
'Environmentally Friendly'?
In order to determine which method of ventilation is most 'environmentally friendly' you must consider what you mean by 'environmentally friendly'.
Many people currently consider this to be 'how much energy does the dwelling use when in use'. However, if we are really looking to save the environment and minimise energy consumption we must also consider the energy used to manufacture, transport, warehouse etc. Of the 3 methods being considered, Passive Stack will last the life of a dwelling as there are no electrical parts to malfunction. However, both of the other methods have electric motors which will have a finite life. When these expire the fan units will need to be replaced. To manufacture these replacements, transport them etc will use energy which will be significant when you consider the whole life of a dwelling.
 
To me this reason shows that Passive Stack is more 'environmentally friendly' and will actually use less energy over the life of a dwelling.
Echoing this, a key Housing Association, along with the BRE and the Housing Corporation, carried out an interesting study which considered this very issue. I have attached a copy for your perusal and would draw your attention to the summary.
 
In conclusion I would recommend carrying out SAP calculations to show the difference in energy use for any particular dwelling you are looking at.
However, when considering the lifetime of the dwelling I would argue that Passive Stack uses less total energy due to not needing any replacements to be manufactured.
 
I hope this is some help. If you require anything further please feel free to call me.

Unfortunately passive stack is uncontrollable and wastes way too much energy (literally up the chimney) for my liking, this is true over any timescale.

Thank you 3LanceElectrician4PartP and Dr T.
 
Interesting views on Passive Stack - I am intrigued by it but have already decided on heat recovery.
 
This will be a second home/holiday let so I need something that runs automatically (eg the kitchen and bathroom fans will be triggered by humidistats), as I don't trust that holiday let visitors will be as obsessed with avoiding damp as I am!
 
My other reasons are that there is a problem with road noise, and my husband and possibly my 2 year old have asthma so clean mould-free, pollen-free air is very important.
 
Holiday homes in general have a tendency to be musty from being left with all the windows closed up for weeks at a time. I am hoping to avoid this.

What material will be used in the hourse?

ITOH and vaillant both do rteasonably inexpensive HRVCs.
 
Unit prices start at about £1,200 (trade) for a small house, to which you would need to add ducting vents etc.