If you have a friend in the UK ask if you can use their address. I did this some years ago - not sure if it still works today. Go to
www.capitalone.co.uk and fill in their online application. You will need to be generous with your answers to give them some confidence. They wanted a copy passport and NI number (you can get a letter on this easily from the local jobs office to the address). If you're lucky they will gve you a credit card within ten days (limit £250). You then use the card a few times, pay it off each month and they will increase the limit for you.
Make sure you settle in full each month. These guys are highway robbers but useful to get your foot on the UK credit ladder.