The dress code is "rainbow hippies attend a fairy tea party". If you aren't sure what that means, go fairly casual but as brightly coloured as possible. Creativity is encouraged, as are hats (top hat, pirate hat, flat cap, wizard hat, any hat).
Please, no black, white, or grey. The brighter the colours the better.
The wedding is fully outdoors, so please consider the weather, it is July in Scotland, so we will be expecting sun, rain, hail, snow, gales, and grey, potentially all at the same time. In the case of rain, there is a parachute over the fire pit, and the ceremony will take place under the trees, so plan your outfit accordingly.
If you still aren't sure, avoid suits and cocktail/ball gowns, and wear whatever the brightest thing in your wardrobe is. Patchwork dungarees, 50's swing dresses, historical clothing, felt waistcoats, pantaloons, and kilts are all good choices.