Can't remove hot tap housing from mixer set

[basill]

I am struggling at removing the hot tap from a set of mixer taps in the bathroom that are pretty similar to the following:

I am pretty sure that something inside the hot tap housing has gone awry as the tap no longer opens fully and I am having fun and games at getting sufficient hot water without the cold tap also being open.

So far I have managed to get the chrome housing and tap end off the hot tap but I cannot turn the brass "nut". The brass metal seems quite soft and after various attempts at using an adjustable spanner on it all I have managed to do is burr the edges of the nut. I even turned a butane gas blow lamp on it hoping that it might free it up but no joy.

Any other ideas? Or am I staring down the barrel of having to replace the entire mixer itself?

 

[MANDATE]

I think you would do better with a solid spanner, either a 'ring' or open ended'. The longer the better. This way you can tap the spanner which generally moves stubborn nuts. You could also apply some penetrating oil which may help.
Most important make sure you're turning the nut anti clockwise.
Now there shouldn't be any but make sure there are no other locking devices such as dowel screws.

 

[PEDANTICVINDICTIVEMAN]

I find an adjustable pipe wrench useful on rounded nuts.

 

[basill]

Thanks for the advice I will give it a go when I am back this weekend.

 

[basill]

Oh a quick stupid question. Is WD40 considered a quality penetrating oil or can you recommend better products?

 

[MANDATE]

One of the best penetrating oils used on rusty nuts/bolts etc is 'plus gas' ( Halfords) but the biggest mistake is not giving it time to penetrate.

 

[basill]

Just a quick update and thanks for the advice guys. The penetrating oil seemed to do the trick although I struggled to find an imperial spanner of the right size so instead resorted to a socket set. I pulled apart the hot water tap assembly and soaked it in descaler, then WD40 and cleaned it all up before greasing the internal bit and putting it all back together along with a new 20p washer for good measure. Works a treat now and the problem with the tap not opening fully and therefore not giving out enough hot water for the shower has been fixed.

Thanks for the advice.