Even if your laptop is working right now, corrosion will most likely progress overtime until the laptop isn't functional. I'd recommend taking it to a professional repairperson with tools to repair water damage (i.e. an ultrasonic cleaner) and have them give it a once over. Since everything is working correctly right now, they probably won't need to replace any components and this will just be preventative maintainence—and it will most likely cost a lot less than £250.