MG ZS water ingress in battery mg uk refusing to repair under warranty .

Owned from new. With full dealer history . Car shut off completely . 131 faults when AA plugged in. Water ingress into battery and connections. . mg are refusing to repair under warranty. Due to a non related plastic undertray having a tiny piece near the wheel arch missing . . Have had confirmation from two other main dealers that this part is in no way there to stop water . I have also pointed out that it's supposed to be ip67 rated and it's never been immersed or in flood water. . . And when asked mg main agent cannot supply full T&C of their 7 year warranty . but mg still refuse to listen. . now reported to the motor ombudsman car has 22000 miles . It's also had the dreaded cracking steering from the start . Had a New rack at 13000 miles and third input shaft at 19000 miles. . faults with the pan roof . And multiple faults with the infotainment etc