Here is a thread on burfords ~ https://www.backyardchickens.com/t/846092/burford-brown
I have to say I don't think your hens are burfords. They are just too light coloured and look to be some other kind of hybrid hen. Burfords are a hybrid with an apparently closely guarded secret to their parentage. From what I've just read many people are passing them off as burfords.
You still have some lovely birds there and if they are hybrids as I think they are they should be good egg layers.