You've not got another remote kicking around which could be interfering have you? Or something in the way of the remote receiver?
It could be the remote, there are cheap Humax Freesat ones on eBay (less than £7).
www.ebay.co.uk/sch/i.html?_from=R40&_nkw=remote+control+humax+foxsat&_sacat=0&LH_TitleDesc=0&_sop=15
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