You have only to read the instructions - or search for them online if you don't have a paper copy.
https://www.espares.co.uk/usermanual/download?userManualId=e5dec47c-b6d4-4155-ad5b-9ffdcc39aa1e
Item 3 on Page 3 says:
If you have no hot water supply....A cold fill adaptor is available from your local Hotpoint authorised Service Centre or by calling the Genuine Parts & Accessories Hotline (see KEY CONTACTS).
It's probably just a Y adapter - something you could cobble up for yourself
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October 2017