Yes there's a group on Fridays at Ackroyd, run by lovely people, beyond that I'm not sure but check on edtots' website! I think there's an informal sing along at crofton park library too but you'd need to check x
Perhaps spend the money that you would have spent on nursery for the next three months on a cleaner if you don't already have one? That way when baby lex is sleeping you won't need to worry about the cleaning and can spend time with seb?