I only fly ex-eus (for work) and so far all has gone fine with this being year 3 of doing this since moving back from abroad. I admit I think about it a lot about what can go wrong (especially the weather as most of my flying is in the winter months) which is really annoying, but I generally build in an overnight in DUB. I have other ways of getting to dub if lhr goes wonky (very rare) such as Ryanair or aer lingus ATR service direct from GLA so I book the 10am to lhr so I can rebook later that day if everything goes wrong, and it sounds like you are just as well planned. I admit I avoid lcy in winter but again you'll be fine and can rebook from lhr if you see lcy is disrupted that day. Don't worry about it (even though we do), you'll be fine! I also use avios for positioning as can be cancelled, although I think that needs to be done 24 hrs in advance, so only useful if lhr is frozen or something!