Next!! They do made to measure and they are so beautifully made. They came to the house and measured and brought them when they were ready ( obviously it isn't next that do this but a sub contracter) .. if you look on their website they have loads of patterns and colours. Have you looked at Laura Ashley? Dunelm ? The range ?
I'd use a local curtain maker - my mum has a curtain shop and has books for half a dozen different fabric suppliers giving a huge range of choice. An experienced curtain maker can also help guide you as to what type of material to choose for your desired look.
I agree on local like Awkwardpaws said. They are generally more expensive but you get what you pay for. I've seen high street bespoke fit and they are fine but just not the same quality. But like all things, depends on budget.
I bought tjhughes and Yorkshire linen duck egg blue Arden pattern as I wanted a countryside theme for my caravan. I got two pairs of 90 by 90 That came to £160 Then I got local seamstresses to shorten then, so for another £54 I got all the lounge curtains barring the door where I went for duck egg chenille as it didn’t want everything the same. I bought a matching throw and cushion as I also had 4 Arden cushions and two plain gold ones. I’ve got loads of fabric left over. I did make the side window myself ( it’s very small) and had to piece the bottom as I didn’t have enough fabric but people will only notice if I tell them
I lol probably make a tablecloth with some of the leftover fabric.
I would definitely go local if I could find the bloody fabric I want. It's a very simple requirement, I want a heavy cream material but with very subtle gold thread through it (we have gold accents elsewhere in the room, and Champagne sort of blinds which I kinda wish we hadn't got because it's bloody impossible to find anything to go with them!)