If you're going to have a honeymoon, decide that first, which fixes the date.
The guest list is what increases the expense. If you're going to have a lot of people, think barbecue or afternoon tea.
Cut all the 'wedding' stuff down. Have a party instead. Register office, second hand dress/suit or outfits you already have, small bunch of flowers to carry, walk to the venue, have that barbecue, sale or return drinks, free glass hire from the supermarket or Majestic. I personally would get a cake from a shop rather than a friend - M&S and other places do standard white-iced cakes you can then decorate.
For the hen/stag do, have a pool tournament at the local - possibly the same one...
Things that you then don't need: bridesmaid's dresses, presents to thank family for all their hard work, £1000 spent on a dress for one day, £800 on a chocolate cake that looks better than you do, professional hair and makeup (why??), some excitingly special form of transport, stag and hen weekends for £500 each, corkage at £7 a bottle, three course sit down meal for which you pay £25 a head including kids who will eat a biscuit, full service bar, dj, band etc etc etc.
Think what really makes a wedding for you, and just have that - ignore the rest.