rayburn 380g - natural gas

[moorlander100]

it was switched off for a couple of days while carrying out work in house. switched back....boiler will light and operates ok. The cooker burner will not light. I can hear the gas valve opening when i turn up the cooker controls..the ingiter works but the pilot on the cooker burner will not stay lit. I have replaced bothe thermocouples as they were looking a bit ropey..but will still not stay lit??
any ideas ??