To answer this question properly....
For a regular customer with a LCD/LED, 3DTV or others, a premium HDMI cable can make an impression of offering more visual quality than a regular one based on his former experience with analog SCART and Component connectors. While it is true that a gold plated premium HDMI is superior to a regular one, it is however so in ways that don't matter that much around consumer electronics - probably the most notable one being maximum bandwidth. While a regular HDMI can achieve maximum transfers of about 10 Gbit/s, a premium one can go as far as 17 Gbit/s or even more. Also, such cables are usually more durable.
Taking into account that a regular HD stream on Freeview uses about 20 Mbit/s (eg. about 500x less than a regular HDMI can theoretically transfer), it is quite clear that even a regular HDMI that meets the official HDMI specifications is quite sufficient by itself.
Conclusion
Although there are applications where a premium gold plated HDMI is advantageous or even required (for professional grade electronics), a regular cheap HDMI is able to offer EXACTLY the same picture quality - meaning lossless. The sales staff in a shop might tell you differently, but then again, sales staff in a shop is paid to sell products.
In other words, there is a difference but it's not worth worrying about