I would be wary of any place which offers to relieve you of a lot of cash.
Retained reflex has little scientific back up in terms of research, I asked Amanda Kirby about it as was tempted to try it last year. She gave it a thumbs down. Youtube for the exercises. I would say only pay if you really want the structure of going and being somewhere each week. Honestly though, you don't need to throw money at dyspraxia. There are TONS of simple things you can try which are of benefit for working on skills.
The Works is an excellent place to pick up bits - pipe cleaners for making funny animals, chalks, blackboard paint (vertical surfaces are good for doing shoulder strength stuff)
When you got diagnosis did the therapists (OT/Physio) give you exercises to work on?
If you give me an idea of the kind of challenges your child has then I am really happy to send you ideas from what we have been given by NHS. There are tons of free resources on youtube too (for example crossing the midline, dough disco) You can look at them and see if age appropriate. There is a good folder called Motor Skills United written by NHS OTs at Stockport. 40 quid I think but covers everything - used at our school. Happy to scan and send you our sheets.
I have so much stuff, I decided to make a sparkle jar so our son can have a lucky dip of a couple of things. Yesterday we made a cave boy assault course - climbing/balancing/crawling/bear walk and finding things and a throwing and drawing game. It doesn't feel like work when you fit the skills to their interests.
The second dip he got was water play - so a nice warm bubble bath and lots of squeezy toys for hand strength - bottles, water pistol etc. Later we did a bit of handwriting shapes and write dance.
Little and often and you will see the improvements.
Our DS is year 4 and was diagnosed Y1.
Have you read the out of synch child has fun?
I can recommend other books. Fantastic dyspraxia website good too.
Ooh and Facebook have various dyspraxia groups for parents have found these really useful.
Time and play are your friends here, not necessarily expensive companies. Get school on board once you have an idea of the things you want to work on. The diagnostic report should detail all the areas of difficulty - visual, spatial awareness, fine motor, gross motor etc.