As for wiring, I like to crimp AND solder the connections. Use only ROSIN CORE (electronic solder) and not too much because if you really saturate the wire beyond the connector it will become too stiff and can break as there is nothing to flex when soaked with solder. What I like to do is slip a piece of the right size heat shrink tubing over the wire and well away from the end to be soldered. Then crimp on an uninsulated connector, solder it on and while still hot rub a bit of HOT MELT glue/sealant all around on the connector barrel and wire/insulation and QUICKLY slide the heat shrink over the connector barrel and glue. Then use a heat gun (or lighter) to further shrink the tubing. Voila! You now have a watertight connection that will last forever (unless using Bosch or Lucas wire or connectors as in an earlier post. Remember Lucas=The Prince Of Darkness!) I've done all the connections on dozens of cars, boats and motorcycles like this and never had a failure even in wet areas.
I used this method when I re-wired the entire engine compartment of my daughter's '87 Volvo which formerly had earth-friendly Bosch
biodegradable wiring.
No joking. Yup, when I cut apart the loom most of the wires had ABSOLUTELY NO INSULATION! I'd turn on the headlights, the engine would stall. Put on the turn signal, the windshield wipers would go on, etc. Not to mention blowing fuses and real bad radio noise! It is all good now and was worth the work but what a pain in the a$$!
When soldering apply heat to the connector/wire (with a clean well-tinned iron) and then add the solder to the barrel of the connector and it should wick right in to the wire. A damp rag or damp sponge makes a handy thing to wipe the excess solder off on when tinning the iron and keeps the tip nice and shiney. It helps to use tinned wire but beware of the "solid tinned" and solid wire, only use stranded for flexibility. Also some wire is not ultraviolet or heat resistant or oil and fuel proof. Best for all around use and rather inexpensive is irradiated PVC. A very good source is old wire looms from your local auto breakers especially the section usually running under the rug going back to the taillights and stuff in the back of the car. Usually this is nice and clean being inside the car and comes in pretty colors. Just check the wire strands with a magnet to make sure it is not steel wire as some car manufacturers cheaped out and didn't want to spend their money on real copper. And don't use wire from 80's Volvos or VWs! I find it is easiest (at least for me) to only use connectors on things that may need to be replaced (relays, etc) and directly solder most connections. If I have to disassemble the bike for some reason I find it just as easy to cut the wire and splice it back together later than to deal with connectors failing. I used to work for a company who was a major supplier for electronics to GM. At the time GM claimed that 85% of all their warranty electronic/electrical failures were due to connector failures!
For you lucky Brits my favorite solder is Ersin Multicore made in the UK, the best there is but hard to find in the US and expensive if it can be found (I have a roll locked up in my workbench just for "special projects") Also use a good grade of PVC or olefin heat shrink tubing, there is some cheap vinyl stuff on the market that not only doesn't shrink as tight, but it splits if you get it too hot and is a pain to use. You get what you pay for. Here in the US, Amateur Radio flea markets (Hamfests) are good places to get all kinds of heat shrink, wire, connectors, etc. I am sure this is true elsewhere too. You might even find some good bike stuff at them, I have!) They usually have some very good military spec. or industrial heat shrink and wire at these things along with tie wraps (zip ties), etc.
Have fun, you WILL learn to enjoy wiring! Just keep repeating after me....
Bosch is German for Lucas. 
