Community Speed Watch (CSW) schemes are by nature very local initiatives, so are best run in conjunction with the parish or town council. For urban areas they can be focused on wards or similarly sized areas. Because police run CSW schemes, they can put individual ones in contact with others in an area to share tips and best practice. In many areas, equipment is shared between different CSW schemes, which can make them very cost effective.
You could consider strengthening a CSW up with a local publicity campaign and pledge to obey speed limits, perhaps even a sticker or sign in cars for drivers who have made the pledge. This could be simply for your community or the wider area.
Where you can't get a CSW off the ground, Speed Indicator Devices (SIDs), which show drivers the speed they are travelling at, are worth considering though that's not to say they can't complement CSW schemes. These can cost a few thousand pounds and unless mounted on street lights (other poles are not strong enough) will cost a further £500 to mount on a special pole. Depending on how much traffic there is, their batteries will need recharging every few days, unless more expensive models with solar panels are used.
Research shows these can be very effective in reducing speeds temporarily - more so than Vehicle Activated Signs that simply light up if a driver is breaking the speed limit. However the impact of a SID at a particular site quickly wears off after a few weeks though in an effect known as ‘regression to mean’, which basically means drivers become used to it. The cost of changing batteries and moving SIDs around are not inconsiderable. More recently some CSW schemes use portable SIDs to show drivers their speed, in addition to taking down the registrations of drivers exceeding the speed limit, something that SIDs cannot do. This avoids the problems of having to mount SIDs.
www.tfl.gov.uk/assets/downloads/effectiveness-of-SIDs.pdf - Study by Transport for London examining the effectiveness of Speed Indicator Devices