DWF Law letter

[Helpplz]

Hi can anyone advise me please. I got a letter from my old employer of 8 months ago that I had been overpaid £459 when I left, as I was on sick leave when handed in my notice, I didn’t realise I had been overpaid and never heard anything until now, I have not acknowledged their letter so I got a letter from dwf law saying that I had to contact them to pay it, but I’ve just blanked their calls and letters now they are saying I have until the end of may to reply but doesn’t state what the action if any would be come end of may ? I live in Scotland they are based in Manchester does this make any difference? I was going to phone them but don’t want to acknowledge it, can I just ignore this or will they take it to court ? Thanks in advance people