Regarding your fear you wouldn’t rent at a higher price point: You are renting a house for max. 5 persons, but on average how large are the groups you rent to?
Take into account that groups of 4 or 5 will prefer a private setup, and will have difficulty finding a place that can accommodate them. Therefor they will be prepared to pay more. If you want to stick to low prices, only stick to them for 1 or 2 persons. If you have more than 1 bedroom, consider making two listings with linked calendars: First listing with all the bedrooms for 3/4/5 people (e.a. £ 70,00 / £ 80,00 / £ 90,00). Second listing with just one bedroom unlocked for 1/2 people (e.a. £ 50,00 / £ 60,00).
Also consider this: If you are now renting the place for 12 days at £ 50,00, you only need to rent 8 days at £ 75,00 to have the same income. Your costs will actually be less, so you will make even more. Just to say that with a higher price, your reservation can take some kind of hit, without affecting your pocket.
On the robes, are there still people using those things? I wouldn’t charge for them. And I wouldn’t offer them for the price point you’re at.