I think if you manage to get enough points, you can fill out the paperwork without any consultant help

It is advised that people apply for immigration within their home country, but you can probably still apply from UK. As for lawyer, check immigration lawyers association like this one http://www.ilpa.org.uk/ for listing

Why do you think there is a ban on you? Anyway probably the best way is to call Immigration direct.

You can not apply for 2 different visas. Just choose what suite you better

well, i think you can do it... I can just give you an example: my wife sister come to visit as in Toronto 2.5 years ago, stay here for 3 month, meet the guy, got married without living Canada, got her PR status in about 5 month and live happily ever after... so it's all up to You really.