We have the same model and I'm interested in other responses to this.
I have included the following in our "People policy FAQs"

Can I claim tax relief for working from home?
Yes! Our business model means you are eligible to claim tax relief for the costs of working from home, such as having a higher energy bill. For tax year 23/24 this is £6 per week or £312 per year. This is done by logging into your Government Gateway Portal and requesting a change to your tax code.

Hi Richard

We recently moved to being a fully remote business and have introduced a system where we will support the reasonable set up of an employees home office but we do not contribute towards household bills, internet etc.

We've essentially said reasonable expenses for things like stationery, printer ink etc. where it's necessary for the performance of the role can be expensed and approved by the line manager up to the value of £100. Larger items such as desk or chair must be approved by HR prior to being purchased and we expect employees to choose something that is of a "suitable standard and durability" and unless a DSE assessment states otherwise we won't contribute towards the cost of new desks/chairs etc. within an 18 month period of the last purchase (expecting that most products will have at least 1 year warranty). We've also provided some examples of furniture we would consider suitable (ie. not just a nice velvet chair that offers no support but will look nice with the interiors).

IT equipment will be provided by the business and employees should contact our IT team for replacements when needed.

For the information around claiming the tax relief we've simply stated the following:

Tax Guidance

It is generally anticipated that, in the vast majority of cases, that the costs of working remotely will be offset by the savings made in both the cost and time of commuting to a Company office in addition to the benefits of an improved work/life balance. Therefore any costs incurred by working remotely will not be met by the Company. It may be possible for employees to claim tax relief from HMRC and information regarding this is available at www.gov.uk.

Hope this helps

In reply to Gemma:

Hi Gemma and Cat, apologies for the delayed reply, just wanted to say thanks - really really helpful and I think I am there with our own policy now :)

Thank you once again! :)