Good luck getting a £3k TV as a replacement for your old one, the 4K series are not a direct replacement, I would envisage this is more likely to be what they would consider a like for like
http://www.lg.com/uk/tvs/lg-55LA660V
Of course the the 65" 4K set wouldn't be a replacement neither would the any 55" set, but said store does have a 60" LG set for £1749 so putting the extra £250 quid to get the 55" 4K set is a definite possibility an extra £1250 for the 65" is pushing my bank balance a bit though.