Edinburgh is all about the cobblestones and the view from the castle. It feels like a movie set, especially when you are wandering the narrow closes of the Old Town. To see it at its best, avoid August. That is when the festivals take over, prices spike, and you can barely move on the Royal Mile. Go in May or September for better weather and actual space to breathe.
A solid trip for a couple usually runs about $2200 for a week of pubs and history. We found a way to handle that cost without paying interest up front. You can break that total into smaller chunks over a year and a half while you plan your route through the Highlands.
The 0% interest period is a deadline, not a permanent discount. If you still have a balance on the card after those 18 months, the standard interest rate will apply to whatever is left. That rate is usually high, so make sure you stay on top of the monthly math.