Welcome to another list of British slang.
Wangle - Some people have all the luck. I know some people that can wangle anything; upgrades on planes, better rooms in hotels. You know what I mean.
Wank - This is the verb to describe the action a wanker participates in.
Wanker - This is a derogatory term used to describe someone who is a bit of a jerk. It actually means someone who masturbates and also has a hand signal that can be done with one hand at people that cannot see you shouting "wanker" at them. This is particularly useful when driving.
Waz - On average, it seems that for every pint of lager you need to go for a waz twice! A complete waste of time in a serious drinking session. It means wee or pee.
Well - Well can be used to accentuate other words. for example someone might be "well hard" to mean he is a real man, as opposed to just "hard". Something really good might be "well good". Or if you were really really pleased with something you might be "well chuffed". Grammatically it's appalling but people say it anyway.
Welly - If you "give it welly", it means you are trying harder or giving it the boot. An example would be when accelerating away from lights, you would give it welly to beat the guy in the mustang convertible in the lane next to you. Welly is also short for wellington boots, which are like your galoshes.
Whinge - Whingers are not popular in any circumstance. To whinge is to whine. We all know someone who likes to whinge about everything.
Willy - Another word for penis. It is the word many young boys are taught as it is a nicer word than most of the alternatives. Some people also use it for girls as there are no nice alternatives. Hence "woman's willy". Also used by grown ups who don't wish to offend (this word is safe to use with elderly Grandparents).
Wind up - This has a couple of meanings. If something you do is a "wind up" it means you are making fun of someone. However it you are "wound up" it means you are annoyed.
Wobbler - To "throw a wobbly" or to "throw a wobbler" means to have a tantrum. Normally happens when you tell your kids they can't have an ice cream or that it's time for bed.
Wonky - If something is shaky or unstable you might say it is wonky. For example I changed my chair in a restaurant recently because I had a wonky one.
Write to - When visiting the US one can't help noticing that you write each other. You don't "write to" each other. Here it would be grammatically incorrect to say "write me" and you would be made to write it out 100 times until you got it right.
Yakking - This means talking incessantly - not that I know anyone who does that now!
Yonks - "Blimey, I haven't heard from you for yonks". If you heard someone say that it would mean that they had not seen you for ages!
Zed - The last letter of the alphabet. The English hate saying zee and only relent with names such as ZZ Top (Zed Zed Top does sound a bit stupid!).
Zonked - If someone is zonked or "zonked out" it means they are totally knackered or you might say exhausted. When a baby has drunk so much milk, his eyes roll into the back of his head, it would be fair to say he was zonked!
Clancy's comment: Yonks, I'm zonked out already, and feeling a bit wonky.