If you are into Doctor Who this place is the best.
They also have an amazing section for stamp and signature collectors, they have signatures from Mother Teresa's to the person that designed Concord. However I am not into that field so I cannot really comment.
I can comment on Doctor Who though :)
This place has the best range of anywhere in London if not beyond. However the range is so big that they cannot have everything and there are a few holes in it. If you want the mainstream things that are available in other places then they may not have it. However if you want the things that are not elsewhere, this place probably has the biggest range anywhere, even including the Doctor Who exhibitions.
The shop is run by proper enthusiasts, they even made the die cast metal items for the new series.
So if you would like Doctor Who or Doctor Who spin off items this place is the best, even better than the Forbidden Planet shop, as this place specialises in those items.
they also have some other things as well such as Thunderbirds, but Doctor Who is their forte. read more