Fair postage promise

I'm conscious of the fact that some of the products I sell are small and light but I'm limited by the functionality of my hosting platform which doesn't allow me to vary delivery prices by weight, so I've had to assume that every delivery will ship as a parcel. However, as an eco-conscious vendor, I try to minimise packaging and some smaller items could be shipped as a letter or large letter (as defined by Royal Mail). Currently, if I use those services, my customers would overpay for delivery based on what it costs me.

My solution to this challenge is to introduce a fair postage promise - if your order can be posted as a letter or large letter, I will automatically adjust the delivery charge and refund the difference between that service and parcel post. Collection from Reading remains free, as does 2nd class delivery of orders above £50 and 1st class delivery of orders above £100.

In the interests of full transparency, my delivery charges include a small contribution towards the cost of specially-sourced sustainable packaging materials, although where possible I re-use packaging as this is environmentally preferable. Overall, my aim is to break even on delivery charges.