Ok guys....here is the low down on the whole thing. Fleece ....you can use any but the best to use i the kempyest rough fleece that you can find as this is easiest to keep air in. However any mix of any fleece is good. You need a depth of about 20cm plus all over your loft....this is a lot of wool as a cubic metre of washed carded/fluffed up wool is approx 16kg.....which will equate to about 28-30kg of unwashed wool or approx 10 fleeces.
It is no good to sling it in the washing machine.....you will damage the machine! The grease needs to be removed and you need at least 60 degrees C plus detergent to do this or it will stay in the fleece and also bung up your drains....I have done this in the past and its not good!
Also a domestic washing machine will not take enough at a time and the cost would be astronomical.....just for 10 fleeces!
Washing by hand is an option but will use huge amounts of hot water.....you need washing soda to get grease out plus good soap and the facilities to spin or otherwise remove the water from the fleece as if left wet for long it will breakdown.....a huge tub, lots of hot water and do it outside!
You have then got to dry it, fluff up and install, along with something to keep insects at bay....they will not attack raw fleece only washed...hence do not eat the wool on the sheep only when made into a jumper carpet etc....they eat the keratin in the wool so need to keep away.
So the effort for 1 cubic metre will take a longlong time!
Commercial scouring can be done, but is expensive and you need to send a lot of wool.....there are a few commercial scourers left in GB and they will charge around 70p per kg...but you need a min of about 500kgs of wool....and need to get it there and collect it....v expensive unless several tons!......and it comes back in unfluffed bales requiring a forklift

Oh and always remember that 40% approx of raw weight of wool goes down the drain....dirt, grease etc

so if sending in 500kg only 250kg approx will come back!
Wool off the sheep is a waste product...actually classified as a grade 3 industrial waste.....that is why farmers get so little for it.....BUT processing is difficult, subject to lots of regs, lots of expense and complicated to explain!