FYI - Hilton have 22 hotels in 'London' (or close enough to be classed as London).
Their website domain is www.hilton.co.uk, so an obvious pointer to the facty this is a scam is the email address they have used. londonhiltonhotel@yahoo.co.uk ????

None but the very smallest businesses in the UK will operate with a Yahoo, Hotmail, or any other webbased email. They will ALL have their own domain names and I wouldnt even reply to anyone unexpected with a Yahoo email adress.

It's not 100% proof of a scam, but its a HUGE indicator and one that everyone should be aware of.