My XK8 1997 had a faulty heater valve and Pump,having no luck finding one,I removed all hoses pump and valve,put one 3/4 inch hose from the top (out) to a normal heater tap (its electric motor control Vintage Air VA50507-VUA Vintage Air Gen-Ii 3 Speed Heater),other side into heater core,other side of heater core back to engine (lower port)I have 2 "T Pieces" also in this line ,one to the fill bottle ,the other to throttle body.
And it works great,heater works great without the pump and I just adjust the temp with the heater tap (electric) .
I have a lot of miles and I think it even runs cooler (not sure why)
Martin

 

Good thinking. You can't beat a double bypass!

 

£110 A$ 246 great not