Hi milge:
I'm in North London. The fact that your dd has started creating her own sign language is fantastic - it means she would probably be quite receptive and sounds quite visual. How is your dd's eye contact - can you 'get in' at all. We had a lot of trouble early on - she would not look at me at all. Does she have any vocalisation?
To be honest makaton is probably cheaper to set up and get started initially. PECS is quite an effort to set up and get going (although some of the other mums here can attest to how much fun a laminator is to have!!) and can be initially quite costly however once you get going it is great.
Another thing I found is that not everyone can understand makaton sign language but most people can understand a picture. Makaton is mostly handy if all the people working with her use it too. Have you thought about nursery placement?
Re: PECS - Have a look on the web - if you go to www.pecs.com (sorry can't do links) there is some information and products available. They do have PECs training courses too although I am not sure how close they come to 'deepest, darkest' Wales. One thing I would say is the sooner you start ANYTHING with her the more likely progress may be seen.
Do you have a speech and language therapist in your area? Someone who is familiar with either makaton or PECS?
Some makaton signs we have found really helpful are "finished" "stop" "waiting".
Both programmes totally have their merits - you just have to decide which one is right for you or try both like we did.
If you want to you can try to contact me via contact another.