Those fume absorbers are just okay. I have some name brand ones and even those didn’t absorb much, you can’t expect much from a 6 mm you can see through, but they did a grand job of spreading the remaining noxious smell about my room. Really the best thing is to exhaust the fumes outdoors so you can share the love with your neighbors, but next best is having something with a lot thicker filter and with more layers. Here’s what I use; they’re really marketed towards marijuana growers in the States and you don’t seem to have much similar in the UK. Try searching for “ventilator kit.” Same basic hardware can be used to exhaust outside. Mine pulls solder smoke from over 50 cm away.

As far as lead-free solder, spend the extra 10 quid and get a name brand such as Kester. The reduction in wasted time and frustration will be well worth it. Also remember to change out your soldering tip when switching between leaded and lead-free; the latter doesn’t work well with lead contamination present.

Whether you need to go lead-free depends in part on your sales volume. If you become the next Mutable Instruments you will definitely need to follow RoHS directives to sell in Europe, but generally at low sales volumes you can get an exemption. I’m not a trade lawyer so you should do your own due diligence in these matters.