Despite the phone only being made available through Apple, Carphone Warehouse and O2 outlets and online, a number of potential purchasers told YouGov that they intend to look elsewhere.
Believing the product, which launches this Friday, will be more widely available, 24% of respondents hoped to buy the iPhone at Phones 4 U, 22% believe it will be available at Dixons, 21% at Curry's and 19% through John Lewis.
Mark Vaygelt, head of technology and telecoms consulting at YouGov, said: "It has not fully registered with the British public that the iPhone will only be available in a small number of stores and online outlets.
"There is an opportunity for well prepared rival retailers and operators to switch potential iPhone customers to other handsets and networks."
The latest findings are part of a second wave of research carried out by YouGov into the marketing and the iPhone before and after its launch.
Previous research carried out last month indicated that the £269 price tag for the handset and the minimum monthly contract of £35 was putting off customers. When surveyed 25% of respondents said there was a high likelihood they would buy the product, however, this slumped to just 1% when they were told the price.
The latest research by YouGov however does indicate that the number of potential customers is growing, with those expressing a high likelihood of purchasing an I-Phone increasing to 3% this month.
The TV ad campaign supporting the launch broke on Monday and was TBWA\Chiat\Day in Los Angeles.