I feel your pain UK_Vstrom after having to repair mine.
After having not ridden my bike for a short period, it appears my throttle is, yet again, sticking slightly open. Open it and let it go, and it'll go back to idle, but it's got a noticeable "sticky" bit right at the point of opening, so if you open it just past that and let it go, it won't go back to idle... until you forcibly roll the throttle back. Didn't notice it when I first went out, but after about 10-15 miles it was becoming very noticeable, almost like heat was making it worse...
Pretty sure it's not the grip/tube, and have wound the cable adjuster off on the pull cable and it's still there, so tank off job tomorrow to have a look and lube everything. Thanks to this forum, seems to be the consensus that removing the tank and checking the throttle linkages is the fix, and realised it's not as big a job as I thought it was after watching youtube!