Consent To Lease On Your Mortgage - Anyone Done This?

I'm on the verge of buying my first property. I'm looking around at different things and getting to know my stuff. I'm going to buy a place and rent it out while I go traveling for two years and then I'll return and live in it. I've just found out that banks do soemthing called "Consent To Lease". The terms of this are different with each bank, but an example with one bank is that they will let you rent out your property on a normal mortgage (don't need a buy to let) for a maximum of three years. After this time, you have to stop renting out the property or else switch to a buy to let mortgage if you want to continue renting it out. Has anyone here done this? It would suit me perfectly as I want to go traveling. I've been reading lots of positive reviews on it.