Hi mate
Is it MOT'd??
If not, I'd do that before doing the head gasket...
You can run it for the interim anyway. And it may not be the head gasket, remember!
1) Cracked rocker cover?
2) leaks from the studs?
3) Any oil lines up there??
I don't know the XBR at all, but try to do one thing at a time. Brakes is a good start. Remember if you need tyres they are not cheap. Silencer by the sound of it?? Leaky fork seals??
You must thing I am a right moany bastard!! I'm not, just saying that if there is expense to come, spend it on things to get you mobile. Remember, as soon as you start stripping the motor, you can no longer use the bike, no matter what state the brakes or silencer is in!!
Cheers! Good luck!
a