Where should you hold the wedding ceremony?  The cheapest option is obviously a Register Office.  Many are located in lovely old buildings, and should not be rejected out of hand.  Check out www.gro.gov.uk for lists of offices and other venues, with details of legal requirements and costs.

Churches are probably the next cheapest, but costs vary according to whether you want an organist, choir, bell ringers etc.

These days there are lots of licensed venues for holding marriages, and these normally offer a combined wedding ceremony and reception package. They are mainly hotels but can be anything from castles to football clubs.  The cost of these vary tremendously and are probably going to be the most expensive, you are paying for the convenience of only having the one location.  There may however be savings that can be off-set, for instance if you are staying in the hotel beforehand you won't need a wedding car, you won't need to decorate two venues with flowers and there may be the possibility of having less photographs (though many specialist wedding photographers only offer set packages).  If lots of your guests will be taking rooms at the venue, try to negotiate discounts or free extras.  This will meet with more success if you are getting married off season or mid-week.  You will not have a much luck if you are getting married on a summer weekend!