I have just had my roof re-slated and I find that a lot of the slates feel loose/floppy under the sarking. I suspect that roofer has made a mistake with the spacing of the battens. If I ignore this what are the long term effects likely to be. The problem is complicated because I am now having solar panels installed.
you could sprayfoam the area to secure the slates,you can purchase it from www.expandingfoamkits.co.uk or have company install it for you. If you leave it, strong winds could dislodge the slates and make it hard to repair because of the installed solar panels.