If you find a lower price online for a direct product match then you should email Dotmaison at customerteam@dotmaison.com to make a price match request. You will need to send a link to the website displaying the lower priced product before the customer team will respond.
Here are a few more things to consider:
The lower price must be a price which is publicly available to all customers, and must be in stock.
The lower priced product needs to be brand new, unused and identical.
The delivery charge is the same or less than Dotmaison.
The seller is UK based and is an authorised reseller (not marketplace) and is not a members only site.