Current construction projects in the UK
An indicator of the state of the economy could be reflected by showing the number of major construction projects that are currently underway at any given time. This information could be obtained from construction projects that are notifiable to the HSE. Mapping this type of notifiable construction project may give an overall visual impression of whats currently going on where and may indicate any regional/national up or downturns.
Current construction projects in the UK
Does this (even partially) help at all?
http://www.glenigan.com/media/monthly_glenigan_index.aspx
Not sure how much value this
Not sure how much value this would add. What is a "major" project, and how do you bring size into it? One £20m project is as valuable as ten £2m project but if all you see is an indicator that there is a project, you lose that.
Also, in terms of impact on the economy right now, it presumably also matters whether it is a £20m project to be done over one year or over three.
Published construction statistics effectively incorporate these points, though, like most statistics that reflect what has actually happened, they come out in arrears. You would not get fine geographical detail either.
So, while opening up the HSE data could add something, I am not convinced it would do what you want it to do.