Thanks for all the great advice. In the end, I had an initial discussion with ex via email. Will be following this up next week (still to decide if F2F or via email - whichever has least emotional build-up).
I dont think I could do mediation with my ex. He is very forceful, very demanding and a PITA.
MrGin - we 'agreed' on access on the day my ex came back from the US - after spending 5 nights there with OW. I was totally unaware that he was with someone else whilst there and that he was even having an affair. He flew back on a Weds morning and that afternoon wanted to discuss putting house on the market and access for DS. I did'nt want to, but he insisted. I plucked 1 night and every other weekend out of the air, he said no, he couldn't live with only seeing DS for such little time, and could we split it so that I had DS for 4 night one week, him 3 nights and then we swap. This is from someone who spent around 10 weeks in total last year on business, who, since splitting in Jan and moving out of tha family home in Jan, has not taken one days a/l to spend with DS (though fair enough he can do as he likes, its his leave). In the end, I backed down to 2 nights and every other weekend. I do feel bullied into this due to emotional circumstances and I was, frankly, scared that he would stop contributing into the house as I was not working and living off my savings as it was (was a SAHM mum, having taken VR, now working full-time, so struggling myself with sudden change in time spent with DS). Emotional surroundings granted and I try to not let it cloud access now, but there was no fair discussion at all. Though the access pattern here would seem fair and most beneficial to DS and his relationship with ex (and also time for me to take off, re-charge etc. So I am totally for access).
I also think that my ex thinks he can take me for a 'mug' a bit as he has had his way (bar overnights since OW, now gf arrived 10 weeks ago - these resume again this week). I am flexible when he goes away on business, but he still seems to think that he should be able to see DS every day (that is when he wants to - as mentioned, he travels a lot with work and is currently taking a lot of personal holidays). This could be possible if I was working p/t, but surely I should get some quality one on one time with DS? I think he is being unreasonable and unrealistic with his demands. He expects me to stay in the local area and if I even moot the idea of moving in the future for work etc, he says that I would be taking DS away from him, which wouldn't be fair etc (needless to say, I keep my future plans to myself now).
notsorted - have managed to reduce the calls to only those days when ex does not see DS and tried to explain that DS is not mad keen at this age to go on the phone, esp as set times as no meaning for him. TBH, the calls were also highly intrusive for me as I would have to stop what I was doing at 7.30am every morning ex wasn't seeing DS (a pain when getting ready for work) and stop whatever we were doing at 7pm for similar evening calls.....My sol had suggested that ex's demands for contact could be down to him proving that he is a good dad, so trying to see it from that perspective as well and less annoyance factor. I dont think he is that concerned with what works for me and DS, just his rights to see his son.
Good idea about googling parenting plans and maybe presenting lots of options. Again, I would need to be forceful in terms of reminding him that there has to be some fluidity here as DS grows, develops, things evolve etc.
ivykaty44 - thanks for the suggestion, but ex would take me at my word and have DS every night (give less maintenance - he is already being strict on this down to the exact number of days he expects to see DS over the course of a year) when it suited him and then hand him back when it didn't.
Again, thanks for all the sterling advice.