The typical number of guests around a table at UK weddings is 8 - which is perfect for your 32 guests as you can get away with just the 4 tables.
However, sometimes the actual table diameters can vary, so 8 may be quite cramped - 6 may be a more suitable alternative and you could opt 4 x 6 seaters and 2 x 7 seaters. However, we strongly advise that you head down to the venue when it is set up for a wedding (usually a Friday night is best and your venue co-ordinator should have no issues with you visiting) so you can judge for yourselves how many guests you can comfortable accomodate around a table.
We do have an article on the site entitled 'Seating Plan for the Guests', which is full of really useful ideas and is well worth a read, so you may wish to check this out.
I hope this helps and best of luck sorting your table plan out (we've been there ourselves, so we don't envy you!).