I suggest that you get on eBay and LFGSS forum to try to find an older steel bike.
I have a Merckx Corsa Extra that has standard diameter tubing (25mm top tube, 28mm seat tube and down tube) which has a spritely ride, with a bit of flex, and also stable geometry (relatively long wheel base). Very comfy bike to ride all day. Weighs 2.1kg for the frame and 700g for the fork.
I also have a Colnago Superissimo Brain which has oversize tubing – oversize as defined in the early 90s. This has a 28mm top tube, 32mm downtube and 28mm seattube. This is a very lively bike with shorter chainstays and wheel base when compared to the Merckx. Still comfy to ride but a bit more “direct” – not quite as straightforward to ride when tired. Weighs 1.8kg for the frame and 650g for the fork, so pretty light despite being essentially lugged, oversize double butted cro-mo.
The problem (in my opinion) with modern steel frames is that they have to pass the CEN test and manufacturers are trying to match the stiffness of carbon frames. This leads to dull and heavy frames.
For a British builder look out for Rourkes. These are all custom, though, so not quite as easy to pick out one or two models.