Possible Clues:

• Opens 22 across in Government for No 10 - for the most part, it's for the cross-border trips perhaps
• Opens 22 across in golf cart - for the most part, it's one for the road on holiday
• Taking king into Agincourt, customised vehicle
• Is open for those going for a drive with first four characters in 26 across with gin cocktail from saloon
• Ruin go-cart, customised vehicle