H.W. cylinder insulation

[torquie]

I would be grateful for an answer to these simple questions.
I have a 20 year-old three bedroomed bungalow, with an airing cupboard containing the gas-fired boiler and the indirect, foam insulated hot water cylinder for water and central heating.
This airing cupboard gets unnecessarily warm so I have recently fitted a Marley (?) four-piece tied-on insulating jacket to the cylinder.

Do I need to cut a hole in this added insulation to help keep the Sunvic clamp-on thermostat cooler?

Is there a recommended temperature setting for this thermostat?

Many thanks.

[steviejoiner74]

Does the cupboard door have a vent on it?
An insulated cylinder wouldn't normally be insulated as the cost of putting a jacket over it might outweigh any potential savings you may make. Especially if the hot water is used frequently.

[torquie]

Oh dear - I thought that I should know whether there is a vent. I will have to sketch it and come back to you.
I am not too bothered about the cost of the added jacket - I just didn't like the thought of the excess heat from the cupboard escaping into the loft.
The water is not used what you might call 'frequently'.
Thanks.

[torquie]

There is a 22mm o.d. copper tube leading from the side of the Ideal Mexico Slimline gas boiler to an open-ended 360 degree turn over a small plastic tank in the loft. So I guess that it is a vented system.
There is a vent in the ceiling of the airing cupboard, leading into the loft.
Should I cut a hole in the extra insulation to help keep the Sunvic clamp-on thermostat cooler?
Thanks.