Im no boiler expert either. However, is your system pressurised from the mains water supply ? Some of them are and have a safety lockout. If this is the case then there will be a pressure gauge and a water supply shut off valve somewhere near it. If you have removed any rads recently then the pressure will of dropped and may need restoring.
Like i said im no expert - im in the cooling trade
Failing that you could try asking here for about £7. Never used the site before but it looks like you post your question and pay some plumber to answer it for you.
http://www.justanswer.com/questions/...f-boiler-seems