@Biggles27 - huge congratulations on your weight loss!
Questions: Is circa £700 your upper limit for a dress? What height are you, what dress size are you, what bits are you happy to show/do you prefer to cover up?
What's your colouring & what colours do you like/suit? Do you want to wear plain or will you consider floral/patterned?
IMO, I think shops that cater for MoBs etc - & wedding dress shops in general - are total & utter style deserts that are full of clothes that are 99% petrochemical byproduct ... I think they are grim - & the clothes are guaranteed to make you look "matronly"! And yes, I know people on here object to words like frumpy, mumsy, matronly etc - but these shops operate in some sort of weird vacuum with obscene mark-ups on mainly not very nice clothes.
If you want to truly celebrate your new figure, springtime & the wedding, you are much better off ignoring anywhere catering for MoBs & looking at Net-a-Porter, The Outnet, MyTheresa, Liberty etc.
There are SO MANY beautiful dresses - in gorgeous fabrics including pure silk & silk blends - to be found, that will be entirely suitable & that will also look up-to-date.