An alternative for a more English garden party feel, is the totally gorgeous Somerset-based White Canvas tent company. Their traditional canvas marquees have a charming, vintage feel and they also provide beautiful printed fabric linings. All this gorgeousness doesn't come cheap though - and they are so busy it's not worth their while travelling up north. Clearly a gap in the market here!
The Raj Tent Club marquees pictured below have an evocative, Maharaja-inspired feel with colourful low seating and block-printed fabric drapes and linings.