Two bathrooms off one combi - one tepid water one hot

[Ruralbliss]

I've (finally) moved into the house I had an offer accepted on last June...

It was built 3 years ago. Family bathroom and en-suite both have showers running off the combi boiler and family bathroom also has a bath.

I cannot get the water to run hot in the family bathroom and yet it is scalding in the en-suite shower.

What might be wrong to cause this? It's really annoying as my teenagers are using my en-suite when I'd looked forward to them having a separate bathroom!

The family bathroom is nearest the combi boiler but not directly above.

Could it be that the routing of the pipe work takes such a long route that it is no longer hot when it gets to the tap?

Probably a thermostatic mixer/temperature limiter fitted for anti scald protection, it is part of building regs. You would need to find it and adjust it, it might be set too low. Otherwise it might be faulty and need a new internal.
It takes cold a hot water and blends them together.

Many thanks @johnd2 I'd come to this conclusion when my teens reported the shower wasn't getting hot and we couldn't get the knob to turn much past the anti-scald button but then I ran my first bath for a soak tonight and found same issue with the bath water.

I'll call a plumber if it's not something I can easily do myself.
I can't see how to easily remove the bath panel as all tiled. Was wondering if there's an adjustable valve to decrease flow rate on both taps to increase heat.

Where’s the mixer tap? It may have an Allen key hole in which case you can take off the fascia and fix the thermostat yourself.

Oooooh thanks @TatianaBis I'll take a look for this. Fearful of flooding the house though!