What are they for then?

Lovers visiting Bakewell write their names on padlocks and attach them to the bridge as a symbol of enduring love.
Our council like a lot of other councils didn't approve and removed them, anyway they're back and I'm not sure if we've really got a problem as this is what it's like on a bridge in Paris.
http://www.blipfoto.com/entry/3545602

Here's a bit of wiki history.
There are varied explanations for the origin of love padlocks. In Europe, love padlocks started appearing in the early 2000s. The reasons love padlocks started to appear vary between locations, and in many instances are unsourced. However, in Rome, the ritual of affixing love padlocks to the bridge Ponte Milvio can be attributed to the 1992 book Three meters above the sky by Italian author Federico Moccia, who later made it into the film-adaptation Tre metri sopra il cielo.
Similarly, an attribution for the bridge Most Ljubavi (lit. the Bridge of Love—now named after the love padlocks) in Serbia exists, where they can be traced to even before World War II. A local schoolmistress named Nada, who was from Vrnjačka Banja, fell in love with a Serbian officer named Relja. After they committed to each other Relja went to war in Greece where he fell in love with a local woman from Corfu. As a consequence, Relja and Nada broke off their engagement. Nada never recovered from that devastating blow, and after some time she died due to heartbreak from her unfortunate love. As young girls from Vrnjačka Banja wanted to protect their own loves, they started writing down their names, together with the names of their loved ones, on padlocks and affixing them to the railings of the bridge where Nada and Relja used to meet.