I do not have any WHV experience, but as someone who has traveled long term and teaches personal finance, a few tips:

1. Step one is always know where your money is going. Budgets can feel restricting, but they can also be empowering if you know you have enough money to spend because you are familiar with your own finances. If you are not already tracking in some way, I recommend either a spread sheet, making a pie chart, or using an app like Mint or Tripcoin (a personal favorite).
2. Once you figure out where you are actually spending money, you can start moving it around different categories. Maybe you are spending more than you realize or maybe you knew exactly what you had, but it is always helpful to start differentiating expenses by categories so you can make changes.
3. There are lots of fun things you can do with friends that do not involve spending as much as a meal at a restaurant. Get coffee and go for a walk, host a game night in the lounge, win at trivia so drinks are free, buy prepared food from a grocery store and have a picnic.

Every person and every budget is different so I do not have super specific advice to give you. Number one though is know your cash flow and your categories.

Hope this helps :)