You can't really run 1/8th Nitro indoors really, (say in a sports hall) because of the fumes, however you could convert to electric (but they can still be VERY noisy LOL). This means racing during the winter is a bit restricted if you don't like the wet/wind/rain and cold.
I would go with electric, since the move to Lipo Packs, recharging from flat is now no longer an issue. Just top up and go!
You can also get started very cheaply racing micro's (1/18th and 1/16th scales) which has all the fun of 1/8th but without the cost.
As has been mentioned, if you want to race, see what the local clubs run. Most probably electric 10th, micro or even SC10 is popular at club level. There is a listing of clubs on the BRCA website (
http://www.brca.org).
HTH
Mark