If you can't make your mortgage payments, or you are worried that you might fall behind because other bills are going up, talk to your mortgage provider as soon as possible. Get in touch with them direct or arrange an appointment with an independent financial advisor to discuss your options.
Make sure that you continue to pay as much as you can manage every month. Keeping up with regular payments, even if they do vary, shows you are committed. Lenders will be more likely to treat you sympathetically and you will reduce the arrears charges at the same time.
You may be eligible for help under a mortgage rescue scheme. In Cardiff some of the Housing Associations offer mortgage rescue so contact them to find out more.