All your questions answed by the good folk at HMRC.
http://www.hmrc.gov.uk/factsheets/ef6.pdf
My favourite part;
"Once the petition has been advertised, other creditors of the company can also join
the proceedings and the company will be responsible for paying costs. These may
increase if the petition is not paid, in full, before the hearing. The hearing takes place at
the High Court in London or the Bristol Registry Court."