There is nothing quite like a firework display to send you on your way as a married couple at the end of the evening reception.
If fireworks are absolutely not an option, consider a release of paper Chinese lanterns. Use a good supplier and test them first - the cheap versions take several minutes to light!
The exact content of a firework display will depend on your own requirements and on the nature of the site. Ideally the display site should be 50 metres long and 25 metres wide for the fireworks themselves, with a fall-out area clear of marquees, cars etc as display fireworks produce quite a bit of debris and ash. Many firework displays reach heights of 100 metres and care should be taken to avoid areas with overhead power cables, trees etc. Your guests should be 50 - 75 metres from the nearest firework, with the wind travelling from the spectators towards the fireworks.
If your budget doesn't run to the £600+ for a six minute professional display, firework companies can supply self-fire packages, with names such as "Feisty Bridesmaid" or "Pageboy Mayhem" which will give a display lasting up to 2 minutes from a single ignition, for less than £100. Obviously, you would need to purchase fireworks that conform to British Standard, from a reputable dealer and follow all safety guidelines.
There is a noise limit of 120 decibels for category 3 fireworks, which are the most powerful fireworks available to the general public. New laws were imposed in October 2004, these were primarily aimed at anti-social use of fireworks, including on the spot fines of £80 for "loutish behaviour". The new Curfew bans the use of fireworks between 11pm-7am. This is extended to 2am-7am on certain nights such as New Years Eve, Chinese New Year and Bonfire Night. Remember, it will be your responsibility to liaise with local authorities and the venue, arrange insurance, ensure that health and safety procedures are adhered to and that there are suitable barriers.