How to do Grafting?

Not sure what you've done - do you mean you've cut off all the lower branches and just left growth at the top to make it a standard? I wouldn't worry too much if that's what you've done - it'll probably be fine.

Standard willows are grafted onto a rrot stock that you would need to get hold of from somewhere. Alot of places only do rootstocks in hundreds so they are probably difficult to get and you would need to find out what variety it is too! the pruning like youve done would work, just keep the stem clear of shoots

i bourght a grafted salix from homebase only £10, i would just buy one as so cheap

But graffted ones do tend to throw a shoot out of the clear 'trunk' and will need removing before it takes over and out competes the grafted variety

not had that prob yet but if anything apears will be nipped off quick