"Ramsey's British Model Trains" suggests that most sets are valued according to their contents.
Ramsey's rough price guide is for mint and mint boxed items. Remember that something is only worh what someone will pay for it!
R.258NS Princess Elizabeth LMS 6201 with Smoke and "Noise". 1971-1974 £25-£35
R.747 LMS 2643 Composite Coach. 1971 1973 £8-£10
R.748 LMS 2640 Brake Coach. 1971 1973 £8-£10
Track and box not listed.
If Box, and contents are in good order, You could be looking at £40-50, but that is only a guesstimate!