You need a hot soldering iron. The hotter the better. You want to melt the solder as quickly as possible and then take the iron away from the job.
Using low temperature means it takes longer to heat the solder and induction heats up the other parts, causing them to melt.

The law is different in the UK. You bought the goods from the trader, not the manufacturer, and the trader is liable for any breaches of contract (unless he was acting as the manufacturer's agent).  Wherever goods are bought they must "conform to contract". This means they must be as described, fit for purpose and of satisfactory quality (i.e. not inherently faulty at the time of sale).
It doesn't matter if you bought it in a sale, your rights are still the same unless the defect was pointed out to you before you bought it.
Contact the retailer.

How old is your transformer? If very old the wiring inside could be perished and may not be safe to use.

Is there a switch on the powerpack that can be moved from 110v to 230v. France uses 230v AC.

Brian Lambert has information and diagrams for bridge rectifiers and powering LEDs on the Electrical Bits section of his website.
http://www.brian-lambert.co.uk/Electrical-2.htm

It is not recommended to run DC locos on DCC as the motors may burn out.
Do your DCC locos actually have decoders fitted or were they described as DCC Ready? DCC Ready locos do not have a decoder fitted.
DC power tracks and power clips may be fitted with a capacitor which will interfere with the DCC 'signal'.

DCC is 22 years old this year, so not that new. There's a new DCC/computer system out this year. Cost around $140.00.
Wonder if Bachmann will follow suit and release their own system, as it's made by their biggest rival in the UK.

It is possible, but not recommended, to run DC locos with some DCC systems. To do so can burn out the motors in the locos, especially when the loco is not moving.

Yes and yes. It has a 6 pin decoder socket. Models11 in the USA have it listed. http://models11.net/cart/

What I'm saying is that the wheels have either not been put on properly in the factory or they have moved later. You don't need to replace the wheels, but adjust them by pulling or pushing on them carefully to get them to the correct distance apart.

Check the back to back distance between the wheels. Should be 7.54 mm.

Yes, that's why it's not recommended to run DC locos on a DCC layout, even if the controller allows you to do it.
The motor of a DC loco can burn out very quickly when the loco is stationary.

You'd be very lucky to get Tri-ang/Hornby Rocket for £50.00 these days. Try tripling the price. They might only sell a thousand in the USA, but they'd be very popular in the UK. I model N scale, but I'd buy one.

Have you seen the series of videos on YouTube?
http://www.youtube.com/watch?v=iqW8J6ecoyk

Yes, it will be fine. The trains use the same 12v DC as US models. It's only the British mains power wallwarts (transformers) that have a different voltage requirement (230v 50hZ). As you will be using the Bachmann 46605A you will not have any problems.