Told I owe money back on my benefits - what worked for you?

After 26 weeks of benefits I got a notice saying I must repay some of it. I do not usually post, so bear with me. The letter mentions an appeal window and a repayment plan. Are payment plans possible?

Thanks for writing this out. I went through something close to it 3 months ago, and it got easier once I kept a simple log of every call and form.