Hi Roy
Probably the way forward is to have a professional take a look and give you an estimate of the cost of any remedial repairs. You can then take a view on the cost/benefit.
If you search the forum, particularly the section on Caravan Servicing and Repairs, you will find a number of companies that specialise in welding and chassis refurbishment. For instance, MPH in Congleton have a good reputation.
It rather depends where you live as to which is most suitable.
Good luck.
Charlie