Podcast cleaning

I've recorded a podcast and the sound quality is awful. It was a noisy environment and I thought it was OK on the sound check but now I've listened back and it's no good. I've tried noise reduction but no good - can anyone fix it?

I don't think it'll be a hugely difficult job for someone more skilled than me - I'm setting a budget of £30 and have attached a sample of the sound. It includes the voices of two people, one of whom's is particularly quiet and drowned out.