Asking prices for British homes fell for the first time this year in July, lowering the annual rate of growth to 3.7 percent from 5.0 percent in June, property website Rightmove showed yesterday. Rightmove blamed the weakening on a rise in the number of homes coming up for sale, which had allowed buyers to gain the upper hand. Rightmove said the supply of properties coming up for sale was up almost 50 percent compared with the same period last year while many buyers were still struggling to get mortgages. It predicted that asking price gains of around 7 percent in the first half of this year would be wiped out by falls in the second half as a public spending squeeze and a weaker economic outlook weigh on confidence