You'd definitely clear UK immigration at T1 on these connections.
LHR tries to do 100% security scanning of pax between flights (except possibly domestic/Ireland connections to domestic/Ireland connections?) so it's no surprise to be security screened on transfer. Soon I think we'll see it enforced for all international transfers, although there are ways around it in some parts of some terminals at the moment.
I would bet that Customs is working behind the scenes on the transfer bags in a way which makes the ultimate green/blue channel decision pretty irrelevant - hence the low priority accorded to it at EDI.