Cavity wall insulation

[LazyDozer]

Our house is a detached 1960s chalet style house (similar to a dormer bungalow) the cavity wall is not closed and has no insulation.
I have access to the cavity in most places.
Should I just chuck some loose eps beads off eBay?
Couple of issues,
Air bricks into cavity and then into suspended wooden floor.
Some outside lights penetrate and cross the cavity with pvc cables.

Do I diy it or just hire a professional. Any thoughts and what should I go for.
Additional the south facing gable end is rendered in K Rend. Can you fill from inside or can it even be effectively patched.
What about foam poured in as a liquid?
Any ideas on cost,
Gable end is 5m wide and full width to 3m then tapers to circa 5m on top of the 3.
Side wall (only one as new wrap around extension on other) is 9m by 3m high.
Zone 6 of London

 

[jeds]

Be careful, a 1960s cavity is likely to be 50mm or less and may be filled with snots, which would make it unsuitable for cavity insulation. Pouring beads in won't work. They just won't fall to the bottom and you won't get an even coverage. An uneven coverage will create cold and warm areas in close proximity and that is a recipe for condensation. My strong advice is get quotes from a reputable cavity insulation company and ask them about checking the cavity?

 

[^woody^]

CWI is notifiable under building regulations, and does require proper assessment of suitability and product type.

 

[LazyDozer]

Thanks a lot! Is there any preference to the better type of CWI? Any recommendations for tradesmen in the Hillingdon area?