DIY Doctor UK DIY Forums

Hi All - I have a shower which is only giving lukewarm water at best. I think the thermostat control needs to be adjusted upwards to allow hotter water. Taking off the circular control knob gives the fitting as shown in the photo. The black plastic around the screw just holds the cover in place. The brass lug showing behind rotates with the spindle until it locates with a stopper on the plastic fitting going into the wall behind it. Can this be adjusted to allow for hotter water? I haven't seen anything like this before and adjustment doesn't seem obvious.

Thanks for any help.