Prob started when jackstarting due to lights.

Prob started when jackstarting due to lights left on, and attaching neg to pos. Sparks flew, and removed quick. Next time car revved itself up and down. Power steerin light and engine light on. THEN BATTERY FIZZLED OUT. Mechanic found 2 blown fuses and car then started ok(previously would not try, perhaps fuses were immobiliser). PS and Engine display on and rev counter not working. CHARGED OVERNIGHT AS MECH said might need more juice to fire up all electrical system. I tried this morning and started fine, and engine light not on any more, but PS and rev still not working. Other fuses may be blown? BATTERY IS QUITE OLD AND MAY BE DAMAGED, SO TRY ALTERNATIVE BATTERY? What do you think?