Starbucks and Costa symbolize two competing companies in the coffee take-out category - the competition compels them to differentiate their brand from the competition, but coffee target groups and consumer trends are still identical for both.
Coffee consumers expect the availability of "their favorite" coffee, in places where they spend time most often. Hence the presence of "coffee islands" in office buildings, or at airports - not only in traditional cafes.
That's also the reason why "ready-made coffee", such as Starbucks, can be found on the shelves of many retail chains. The consumer trend of searching for natural products is also significantly emphasized. In turn, this is addressed by both chains, e.g. in the appearance of their cafes or islands, both in the arrangement, graphics or font, but also in the finishing materials, such as wood.
The picture shows examples of the activities discussed above - two islands of two competing brands which both look very similar.