Need a bit of advice about the best way of removing allen bolts or screws.
I'm having difficulty removing one of the bolts which clamps the fork leg in the lower triple tree. Seems to have seized in the aluminium. Also trying to remove the smaller bolts that hold the floating disc onto the front wheel.
Afraid of rounding off the bolt holes.
What's the best method? Heat? Would a gas blowtorch be sufficient?
Or what about an impact driver?
Suggestions please.

I would avoid using an impact driver because it could tear off the thread..
First think to do is to is to hit the screw with a good blow (Use a punch that fits into the hex of the head). sometimes a good blow will be enough to 'unseize' the thread and you will be able to slack the screw. If you are successful with this method, slack the screw by 1/8 to 1/4 turn and then poor some penetrating oil over night.
If this doesn't work, the torch is the second option. You will have to give a very quick heat to the aluminum and then a good blow on the screw. Aluminum expands quicker and to a higher ratio than steel. The reason for a quick heat is to expand the aluminum without expanding the steel.

Hi,
I would suggest the use of penetrating oil made from a 50% mix of acetone and ATF and let it soak. It sometimes takes an overnight soak and then as Bert says a couple of good whacks to break the hold of the corrosion which has probably locked the screw in place.
Regards,
K-BIKE

i have always found it usefull to try tightening before loosening when finding a stuck bolt ........ after tightening ..give the head of the bolt a little whack with a hammer ...often the retensioning of the bolt stores some energy and then the whack will release the threads a touch ......enough to start undoing at least .......just a thought....