I like using belts to ensure flat cake tops however I struggle with temperature & cooking times.  I usually use 10/12 " tins & bake around 160c for 1 hour before checking & essentially guessing fro. How it looks if it may be baked.  Should I use a normal oven temp of 180c & just bake longer which I have tried but failed.  I just added 10 mins extra to the baking time but the centre wasn't cooked & my cake sank.  Can anyone kindly offer any suggestions as it's very frustrating.  Thankyou in advance 

I rarely use the baking strips anymore because it takes so much longer to bake, and like you, with mixed results.  I prefer to bake at a lower temperature,  325 degrees F (a little more than 160 c) which does require 10 or 15 extra minutes, without the baking strips.  I get very little doming at this temperature.  When I bake 10" and 12" layers, I use multiple baking nails in each pan, as well.  

I've never used the baking strips or even flower nails in my larger cakes and I've never had a problem. I also never cook by time, just by smell. As long as you're cooking at a low enough temp to ensure it cooks all the way through, just cook until it smells wonderful and check the top. If you don't leave finger dents in the top, it's done. If you prefer to cook by time, take note of how long you cooked it and you're all good.

Much like the other posters here I seldom used baking strips on round pans but did on the corners of squars.  Seldom even used flower nails - even on cakes up to 16".    Like cakefan92 I mostly judge how done my cakes are by smell, using low temps and pull them before they start to pull away from the sides of the pan. 

Another thought - have you had your oven checked?  The temp might be off.  Get a good quality thermometer to check it.  I know in the US repairmen can check it - sometimes for no charge. 

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