macbook pro early 2013 15" graphics card issue

Hello, I have a -

MacBook Pro (Retina, 15-inch, Early 2013)

Processor 2.4 GHz Intel Core i7

Memory GB 1600 MHz DDR3

Start up Disk Macintosh HD

Graphics Intel HD Graphics 4000 1536 MB

mac OS High Sierra version 10.13.3 (17D102)

This MacBook has now developed the graphics card issue that causes my machine to crash or switch off when it gets slightly hot, or when switching over to the NVIDIA GeForce graphics card. I took my MacBook pro to my nearest Apple store and was quoted £465 plus vat to replace the logic board. I can't afford to pay this amount at the moment. I am also too late for the replacement programme and was also informed that because my MacBook pro was bought from an apple re-seller, not an apple store, it isn't fully covered by apple's adherence to uk consumer law. Is there a work-around to enable me to keep my MacBook cooler to stop it from crashing? Would a cooling mat help? I do quite a bit of illustrating with my mac and need to use the higher graphics card.