Recently I was offered work here and applied for and was granted a non B visa (multiple entry one year). Unfortunately the promised job offer didn't materialise, so nothing further has happened, and nothing has gone ahead regarding work permit etc. Presumably in this situation there's no problem me being here on this visa (there's no reference in my passport to the original sponsor?)

Also if I was to get future employment offers, can a WP be applied for on the basis of this non B?

No/Yes