Vaillant VCW T3W - Start up problem?

Hello friends, I hope that you can give me some advice. I have a virtually unused Vaillant VCW T3W installed in a chalet in Merseyside. Everything has been turned off for some time. I have turned the propane back on, have the water flowing through it and the pilot light lit, but nothing happens when I turn the tap or the heating on. Is the a procedure that I can go through to eliminate or identify faults? Any help or advice very much appreciated. Kind regards, Eddie.