Large bottles are available at all of the following:

Amazon UK online.

Bottle and Jug dept., Farm road, Worthing

Custom spirit co., Handcross road, Horsham (Vermouth only)

Creoate online

Fletching village stores, High street, Fletching (Vermouth only)

Foodmarket online

Grape and grain, the Broadway, Haywards heath

Hollington wine company online

National trust London/SE sites inc. Birling gap and the Seven sisters, Chartwell, Knole, Sheffield park and garden, Sissinghurst castle garden and Standen house and garden.

Sarah's cellar, High street, Battle.

Sip and share online

Quaff, Fiveways and Hove store (Vermouth only)

Wermut bar, Heist market, St-Leonards-on-sea, Hastings (Vermouth only)

Yumbles online

And via Burgundy wines ltd. a.k.a. Sussex winehouse (Vermouth only)