There are thousands of design agencies around the UK ranging from small design studios employing a couple of people; up to top London firms working with global brands.
Finding the right sort of agency for your business is something that could take time.
If you are thinking about using a brochure designer to produce a new brochure/catalog/directory then there a few things that need to be considered before you make your decision.
Use a local design agency where possible
Use a designer that knows a bit about your industry and market place
Compare prices from a few designers to ensure you get the best deal.
As there are thousands of brochure designers in the UK, it makes good sense to work with someone local as opposed to a designer that is 100's of miles away.
It is advised to always where possible meet with a designer - as you will be able to get a much better result. If you are in front of a designer - you know they are 100% focused on you and your requirement (as opposed to working via e-mail they may just be rushing something together to get you sorted and out the door). Also, you do not know if they are actually based in India and just say on their UK website that they are based here by visiting them you will know who they are and what they claim is true.
There is a big advantage in working with a designer that knows your industry - they will have a cleared understanding of designs that work and do not work in your market. Also, they may be able to give insights as to what other companies in your market are doing (that works) and transferring ideas to you - giving you a head start.
Brochure design costs can vary a lot from designer to designer. With design there is no industry standard, all designers charge what they want (or can get away with) so depending on the size of the agency, how much their over heads are, how many cars the MD has - the costs will vary massively.
Using a comparison site cam give you design idea and quotes from local designers saving you time and effort in hunting around.