The copper tails were probably supplied as part of the mixer tap and are generally thought of as better than flexis, (which are only rubber pipes with outer metal braiding to prevent them bursting.) So the copper tails are good and your B&Q are obviously wrong.
The silicone might have been done by the installer to try to be belt & braces with sealing the mixer to sink.
The soldering is typically a bit rough, but one thing I consider is a bodge is that the copper tails have been connected by soldered fittings to your pipework. Really should be fittings that can be uncoupled, - like brass compression fittings IMO. But no law against soldering directly to the copper tails, just daft though.