Not speaking from experience in any dealings; be aware though that retailers are not obliged to offer refunds just because you, 'change your mind'. Unless the goods provided were faulty for reason(s) under the sale of goods act 1979 (as amended) i.e. not fit for purpose or not as described etc.... then the retailer is not compelled to offer you a refund.
If you do decide to go ahead try not to use Paypal; agree and obtain the written quotation i.e. itemised sizes, specification, quality, timescale, price of goods beforehand. Otherwise using Paypal would mean the transaction has not taken place directly between the supplier and yourself, this would void the section 75 liability.... due to a third party payment merchant being involved in the transaction.
Instead if possible, pay the retailer directly for this transaction by using your credit card to pay for the order, that way you will have the valuable free protection offered by courtesy of section 75 of the consumer credit act 1974. This would at least entitle you to a chargeback from your credit card issuer should the retailer breach the contract with you. (none delivery. goods not as agreed in written quotation, failure or bankruptcy of supplier etc etc..)
**Also be aware the protection of the DSR's Distance Selling Regulations does not apply to goods supplied that are of a personalised nature. These made to measure and personal spec dresses would certainly fall under that category!