How can I mend my BT4600 (1+1) phone?

BT4600 phone system (1+1). I have switched off the power to my phone system and not realised it . Away for a few days and spotted this on my return. Switched on power to system again and cannot get it to work. I left on for 24 hours to re charge, but does not seem to be re charging as 'C' message just appears on the base unit. I am not getting any display on the main handset or the extension handset. All I get is a pulsing on both handset displays but nothing else on the screens. I have replaced the rechargeabe batteries in both handsets but this has had no effect. What should I try next