Is the budget £1,500 a week or £1,500 a month, OP?
For south of London, if it's monthly, it'll be tight imo. If weekly, it should be easy!
I must admit, I assumed it was monthly, but if it was weekly you could look at towns like Lewes and Haywards Heath, both on the Thameslink, so direct to Blackfriars. Train fare is around £60 a day, less if your husband can start late enough to get a train that leaves after 9.30.
If it's monthly, you'd probably have to look east, in Kent, where rents tend to be cheaper. Faversham is nice, but I suspect rents will high-ish. The Medway towns (Chatham, Gillingham, Rochester, Strood and one another I can never remember) used to be grim, but I believe they have improved quite a lot.
I think you might do better to consider the outer London suburbs, where travel costs will be lower but in some areas, rents aren't much different from commuter towns a lot further out.
Avoid Croydon though. It's cheap for a reason.