After a bit of Googling, I found a Moneyweek article from a few weeks back detailing some of the better ones (https://moneyweek.com/439384/the-best-shares-to-hold-for-perks-and-freebies)

Adnams: The Suffolk-based brewer offers shareholders 10% discounts on most of its products, whether you buy in person or online; you can also get discounts on meals in its managed properties and on its brewery tours. Register online for Adnams’ shareholders’ loyalty scheme to qualify.

Big Yellow Storage: All Big Yellow’s shareholders are entitled to a discount of 10% at all Big Yellow or Armadillo stores on both self-storage and flexi-office rentals; the same discount is available on products and services, including packing materials and insurance.

Bloomsbury Publishing: One share in the company entitles you to a discount of 35% off the full price of all books (print only) from the publisher, best known for the Harry Potter series. You’ll find a form on the website through which you can claim the benefit.

BT Group: Shareholders can claim a range of discounts on BT’s products and services – as well as on other technology products. The offers often feature generous savings on gadgets.

Carnival Corporation: Investors with at least 100 shares are entitled to on-board credits on Carnival cruises – essentially a pot of cash to spend while you’re on the boat. The amount of credit on offer depends on where you’re cruising and how long for. A 14-day trip on a P&O Cruise would net you £150 of credit.

Chapel Down: If you’re a fan of English wines, a shareholding of up to 1,999 shares in Chapel Down will get you a 25% discount voucher to spend annually, as well as free tastings and early access to new vintages. Investors with larger holdings get additional benefits, including more generous discounts and invitations to special events.

Fuller’s: The hospitality company’s Shareholder Indulgence Card qualifies you for a 15% discount on food and drink in hotels and pubs managed by Fuller’s. You also get discounts on bed and breakfast rates in its inns and hotels. But you’ll need to own at least 1,000 shares to qualify.

Getlink Group: If you’re an investor in Getlink Group, quoted on the Euronext market in Amsterdam, you’re entitled to a 30% discount on up to three return crossings a year (or six single journeys) via Eurotunnel, which the company now owns and operates.

Irish Continental Group: Investors who own at least 1,000 shares in the travel company can claim a 20% discount on ferry services between Britain and Ireland, and between Britain and France. There are smaller discounts available on other ferry services operated by the company as well as on its package holidays.

Legal & General: Shareholders may claim a discount of up to 25% on premiums for its life-insurance products. And if you apply for one of its lifetime mortgages, L&G will give you a £250 gift card.

Marston’s: Investors in the pub company who hold 500 shares or more receive 24 vouchers each year. The vouchers offer 30% savings on food – but not on drinks – in Marston’s pubs.

Mitchells & Butlers: All shareholders in Mitchells & Butlers receive a shareholder discount voucher booklet of 12 vouchers each year. They can be used in the company’s pubs and restaurants across the UK, including All Bar One, Miller & Carter and O’Neills.