Today's Euston would have looked far too modern for the 1940s! Mind you I don't think the old Euston looked much like Kings Cross.
No the old Euston had no resemblance at all to King's Cross and there were several other anachronisms in the film. As already mentioned the overhead catenary was not installed until the 1970's and they were using 1950's Mark I stock to represent 1940 (I did however notice a railwayman with an LMS cap badge). I doubt that Tippex correcting fluid was available in 1951, and the leading actress could not pronounce the name of the Swiss mathematician Euler.
The sets and locations were far too twee and manicured and lacked the authentic grime and shabbiness of 1940s and 1950s Britain. The dialogue and mannerisms were those of the 21st century....people did not speak or act like that in the 1940s and 1950s.
I feel I may be 'nit picking' and after about 20 minutes of this decided I would just enjoy the film for what it is....... a very good film! After all most younger people will be quite unaware of any of the above short comings! I have lived too long!
Incidentally most of the screen play corresponds quite closely with Andrew Hodges excellent and very detailed biography of Alan Turing and this is an impressive achievement. Difficult to see how they could have crammed any more into 2 hours entertainment.