Lens advice for Indoor use

[Spoolio]

I'm after a lens for my EOS 40D to use indoors primarily for RC shots, so sports halls will be the norm. Light conditions will vary from passable (Worksop) to dim yellow tungsten. The other problem is I have a mortgage to pay so mega-money stuff is out of the question. Any recommendations would be appreciated. I've got a kit 17-85 EF-S IS USM lens and it's OK generally but it did really struggle at Worksop. My other lens (Canon 70-300 IS USM) is OK outside on a good day but it's total pap indoors.