european pension/sickness benefit claim

Can anyone advise? I worked and paid insurance contributions in Germany for a number of years. I have since returned to Britain and have worked and paid insurance contributions too. I now have a diagnosed progressive illness and have been in receipt of ESA for a year now. I hope to receive a small company pension from one or two companies I have previously been employed with. I have also applied to Germany (apparently I can receive a reduced state pension,with disability, and am over 55 yrs.) Newcastle, the international section, have since received wind off this and are insisting on any backpayments I might receive from Germany
should be refunded to DWP in Britain. I find it difficult to understand how the system works. If I have worked and contributed long enough to receive ESA in Brtiain then why should any contributions made elsewhere come into the equation ? I feel severely penalised if this is the case. Anyone else in Britain receives the same for less. That makes my British contributions worth nothing. How can this be correct? Any ideas ?