How do we keep investors interested in UK property?-

An incentive for them to invest in order to generate a good public image for themsleves/ company.
For example, if the property is to be rented or sold at a later date, then a portion of the profit could go towards helping someone. E.g. money towards supporting new construction companies, helping homeless, funding overseas project in developing countries etc.
With the right advertising and public awareness made it could consequently boost sales for the investor's company.

Another idea could be to have the option for people to invest money in the building in return for a mrgin of profit when sold. Similar to the website Kickstarter where anybody can invest a bit of money if they think the idea is good. So anybody can invest in a buidling if they think it could sell for a lot at a later date. A site where people interested in investing in UK property can go to invest a bit of money, if they see enough investors intertested it will generate momentum.