You 'bought' the phone from the Orange shop, and that's where you go for satisfaction under the sale of goods act.
Now the problem
Under the terms of the act the shop has the option to repair the phone. There's no obligation for them to lend you one while yours is being repaired, and of course they will not be doing the repair themselves. They'll send the phone to a repair centre, and again under the terms of the act they may take a 'reasonable' amount of time to do it. What is 'reasonable' is not defined in the act - each case is considered on its merits as it comes to court.
To be honest, the shortest line between A & B in these circumstances is probably the one suggested by TechMad. Unless you have another phone (left over from a previous upgrade) you could buy the cheapest possible 'Pay as you go' phone from Prange and put your contract SIM card in it. The SIM card will not be required to repair a fascia light problem, and you'll be able to phone normally while the repair's under way.