S75 is not crucial for 99% of your payments by volume, unless there is a reason I may need to get a refund off Starbucks.

credit rating - come on, how old are you? In the UK the average member of a frequent flyer scheme is 46 years old (Virgin Atlantic data), average income high. I know what % of UK cobrand credit cardholders ever pay interest and it is not far off zero. Credit rating concerns are for 21 year olds in £25k jobs. In any case you are unlikely to use Marriott as your primary card in the UK.