Do u know Sensational Marketing Campaign? that's what i called it !
Example: Build The Largest Handbags on Guinness worlds Record or the most Valueable Handbags with diamond/sapphire/diamond on it .....etc
Result: your Brands will get covered up by media around the Worlds!!!
You can Boost your campaign with PR to expanded Your Brands

There are agencies that have relationships with major social media influencers with certainly some that are followed for their fashion sense and tips. Reach out to these agencies to target. You can target those influencers within your budget (obviously, the more "sway" the more expensive). Of course, they take in-kind compensation, so you may be able to "pay" the influencers compensation strictly with merchandise. It is not traditional "press," but is a lot more relevant.

Retailers always want a proven product with an existing demand. Even if you do get it on the shelves, if the handbag doesn't sell, they won't keep you on the shelves very long.

Depends on your marketing budget, I think your best bet is partner up with social media influencers (especially instagrammers with a large following in UK), get them to endorse and showcase your products and drive them to a simple ecommerce funnel.

Once you have a proven sales record, then you can take your numbers to the retailers.

Now you are not begging them to take your products, you are saying, "Hey, I've got this handbag that's selling so well online, I think your customers would want to buy it in your store as well. How many do you want to carry?"