Vauxhall Corsa build up of cabin pressure

Please help me!! I have a 55 reg Vauxhall Corsa sri & in the last month i have been experiencing strange air tight pressure or a build up of vibrations that you can’t hear but you can feel in the car. Of course 3 weeks after the warranty has run out!! The pressure is bad when you get in the car & shut the door you can feel your ears tense. It’s almost like your taking off in an airoplane. It seems get worse with the faster you go & between 40mph & 60mph you feel like your head could explode & your ears pop. When you turn the heater on anymore than no.2 then it’s terrible, but there is no noise or whirring sounds??.... I have now taken to driving with my windows open a little & in this weather its not good at all, but still doesn’t make a great deal of difference. This last week I have been driving whilst sitting on a cushion which has helped but not overly much. I have asked many mechanics & they’re all baffled & can’t work out what it could be. All filters are clean, I have tightened my doors so it’s not coming through them...??? I had new tyre’s & brakes fitted on the 18th October but I have tried a different set of wheels but again makes no difference. Iv taken it to a local garage 2day & they think the exhaust is rattling at a higher pace than it should as it enters in to the engine & says its unfixable...???? My local dealer where my warranty work was carried out at are absolutely hopeless & I would never have another Vauxhall again as the service has been so poor. I’m at my last resort as this has now gone on for a month but am reluctant to trade it in. I also not afford to keep taking it different garages for them to charge me to look at it. I have now in total taken it to 4 garages & numerous people are baffled by it. What can i do?..... It’s now starting to distress me. I’d be grateful of any suggestions.

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