My CH boiler keeps blowing out when its windy outside!?

Hi, I hope someone can help me with this one. I have an old Baxi Wm 381 RS CH boiler in a house we just moved in to. It works fine(mostly) when the weather outside is ok but as soon as we get any amount of wind, the gas flame goes out - including the pilot light. At this point, you can smell gas around the unit when i go to the boiler which is located at the top of the steps down to our cellar. What i usually do is just switch the power off at the timer, turn the gas on/off valve so the gas is off and turn the gas control(size of flame) valve to its off position and then try and cycle it back to a running state again - unless the wind blows it out and then i give up for the day. When it goes out, you hear a solenoid click which is when we know it is too windy for our boiler - so no heating today!
The CH is a VERY simple set up. No hot water, just rads. No room thermostat, just an electro mechanical twice a day timer turning the boiler on and off. There are no TRVs on the rads so the whole system is either heating - or not.
The whole CH system is in need of an overhaul. It is all connected by 8mm(or less?) small bore some of which is leaking air at the rad joints, as you can often hear the pump pushing air around with the water. The pump iself also very slowly drips the odd drip of water and looks generally corroded. none of this seems to stop the system working in good weather however!
The flue? its just a hole through the wall to the street outside with a metal cover over it. We are in a 2 up 2 down end terrace in chilly, windy Burnley.
We had a gas engineer out for something else and he muttered something about the 'Gasket'? needing to be replaced. Before it blows out, you can see the gas jets blowing around and partly blowing out until they relight when the wind dies. Is the gasket something to do with keeping the exhaust gasses going out but keeping the elements from blowing in? If so how hard is it to replace and where is the gasket? I imagine it involves removing and dismantling the whole boiler to get to the gasket?
Also, when i get round to upgrading the whole CH system, am i better off replacing the 8mm small bore with 12mm(half inch?) - would the whole house heat up faster then? It takes a good 2 hours running to get the house just about warm and although the rads are hot to the touch and heat up fast, they are never REALLY hot like in some peoples houses(none of the pipes are insulated)
One more thing(just one!) The gas control valve does not work. It is supoposed to vary the size of the flame from High in winter to Low in summer, according to how you set the control knob. It has worked once when i was fiddling with it but normally just stays at its max flame height. I would like this to work as i beleive having the CH on a medium setting all day is probably more cost effective than having our waste of space/gas brand new coal effect gas fire on full blast in one room all day. Is this simple to fix/replace?
I am considering a gas boiler/solid fuel cast iron stove/backboiler combi system of my own design at some point so the gas will be the back up but the CH AND hot water will be heated by wood/coal fire eventually - but until then, I need my baxi boiler working! Can anyone help? Thankyou! email: acotterill.walshaw@webmail.digitalbrain.com