Hi Helpmeplease
If you are only receiving Contribution Based ESA then the payment should be treated as a one-off payment of capital so your ESA(CB) will not be affected and you do not need to tell the DWP.
As you have stated you are receiving Income Related ESA then if the payment will take you above the £6000 limit there may be deductions from your ESA(IR). If as a result of the payment your total savings and assets exceed £16.000 then your ESA(IR) will stop.
I would advise you to seek help from your local Welfare Rights Organisation who will be able to take all your circumstances into consideration; you can find your local Welfare Rights Organisation to help you with advice by clicking on the link below and putting in your post code, it will then come up with a MAP with a list of agencies.
advicelocal.uk Gary