Yes it's easy, no tax on foreign income, no tax on foreign capital gains, no tax on dividends, you only pay taxes if you work for someone in Gib.
Apartments are cheap or expensive depending on the are, or you can always rent a room just to have an address in Gib.
You cross the border in 5 minutes and you go to Spain, no one will know if you are in Gib or in Spain, you get on a plane from Gib to London and from London to anywhere in the world (less expensive than if you fly from Málaga airport which is always a possibility but you would have to fly to Madrid or to any other Capital in order to fly somewhere else, so don't bother flying from Málaga airport, take off from Gib to London and that's it! Málaga airport is about 1h45' from Gib by car.)
I wish people wouldn't give the wrong information, there are several ways to get residency in Gib, I don't have time to get into all the details but you can find then online.