Retrofit improvement schemes. I really hope this isn't an example of what's to come. 

Re downpipe , few weeks ago I was asked to repair a leaking gutter joint and discovered that the downpipe lead straight into the soil I dug and dug but no drain or soakaway could be found so for probably 40 years the water just overflowed the gutter as the downpipe entered compacted clay (an effective plug) . Only a small roof so piped onto garden as far away as possible.

I wonder how much air trickles through those trickle vents? Not a lot, I imagine!