Crick was perhaps halfway into a Ph.D. in physics when the war broke out, during which he basically did very applied physics for the British. After the war, he did a Ph.D. under Max Perutz on X-ray diffraction. Crystallography is very useful in biology, but it is itself very far from a biological topic. Crick wrote of experiencing extreme impedance mismatch when he switched from physics to biology and, perhaps most significantly, Watson often referred to Crick as 'the physicist' or to 'having him do the physics' (sorry, I don't have the full text in front of me) in The Double Helix, suggesting that his approach to biological problems was primarily a physical one. It is true that Crick did work under the Medical Research Council, but it is somewhat misleading to say that he was doing medical research in the conventional sense. He was studying the biophysics of cytoplasm, which is not something that people trained in medicine do.

I admit that Hodgkin and Huxley are harder cases: both had early inclinations to physics and then got sidetracked into physiology. Both of them spent the war doing things you'd have a physicist doing during a war, and afterwards did their their famous work on the action potential. I read the Hodgkin and Huxley papers, but I read them in a course in the math department-- they contain some of history's finest examples of mathematical modeling, relying heavily on dynamical systems and circuit theory. It is a regrettably rare biologist who wants to go near those papers. It is manifestly not the work of traditionally trained biologists.

Disciplinary boundaries in mid-century Britain were somewhat different then, and I realize the danger of playing No True Biologist. But the mainstream of biology is only very recently acknowledging the importance of the physical approach: Hodgkin and Huxley could have been Hodgkin and Huxley without a lick of genetics or ethology, but they couldn't have been Hodgkin and Huxley without the cable equation.