Sporadic pilot light failure Worcester 240 Combi

[bus2inop]

We have had the above boiler for 8 1/2 years. It has recently developed a sporadic fault of the pilot light going out. I pressin the grey gas valve for a few seconds and then it takes a few clicks of the red button to re-ignite the pilot light.
Does anyone have any suggestions as to what is causing this fault. The boiler up to now has been very reliable and only required a new diaphragm 2 years ago. There doesn't seem to be any specific pattern to it going out. It did it on a few consecutive days and then went a week or so without any problems; does something just need cleaning. The boiler is in our airing cupboard and I recently lined the inner doors with some heat insulating material. I can't remember though if the problem started before or after I insulated the cupboard doors.
many thanks to anyone who can help!!!!!!!

 

[ollski]

Probably needs a service to clean the c%$p out of the pilot which is reducing your pilot flame size, in turn not heating the thermocouple and knocking off the gas supply.
I don't have a manual here for that model but there may be some relevance in the compartment ventilation section of the installation manual.

 

[COG]

as above ,but the 240 has a limit stat that intrupts the pilot this can fail with time so best have it replaced when you get the boiler serviced as not expensive. the compartment ventillation for the 240 should be around 42 sq in at the top and at the bottom , thats into the room..I assume its balanced flue

 

[bus2inop]

To Olskii and Cog,
Cheers for your advise I'll have it done immediately.
Bus2inop