Very difficult to compare economies historically because of the fluctuations in exchange rates but I found this:
https://en.m.wikipedia.org/wiki/Angus_Maddison_statistics_of_the_ten_largest_economies_by_GDP_(PPP)
I seem to remember that we were vying for fourth with Italy of all countries for quite a time. As far as growth is concerned we have done comparatively very well since the start of the Single Market, in fact Britain has thrived. That will no longer be the case.