Afternoon, thanks again for the replies, I'm a bit calmer today than I was yesterday.
I don't necessarily want to stop contact, just stop the way it is and the way it affects the ds's as it's really not healthy for them, emotionally and physically. Of course life would be so much easier without him around but ultimately he is their dad even if he's never acted in such a way. I find it difficult on a personal level because I really do hate him, he makes my skin crawl and I hate that indirectly he still has control over me. In a way I'm quite jealous of how DH never has to have any contact with his ex. Yes they were married but he had to find her o get her permission for the divorce but that was the 1st contact he'd had in several years and he has had none since and never needs to have contact with her again, I'd love to have that but of course big birthdays, weddings, grandchildrens birthdays etc he's still going to be there haunting me.
hairy They are 9 & 5, have been seperated from ex for 4 years so ds2 is too young to remember us all living in the same house. Both children have seen someone at CAMHS for different reasons and she has said that the change in expectations etc at home and at his is no good for ds2 especially (suspected ADHD) but says she is not allowed to get involved with courts etc. It is written extensively in ds2s notes at gp that his health is being affected by being around there (heavy smoke which gives him a bad cough and swells his tonsils up, plus fed foods that he is intolerat to so his behaviour is impossible to deal with).
Sara I know what you mean, we do to an extent, they come home at 4pm which is the latest that ex will have them to. So it's a case of dinner, bath & early to bed (they have extremely late nights so eed the extra sleep). We used to take them to the park to get the pent up energy out of them but they forget how to behave and as a result can't take them where other people may be.
privatename, that was MILs suggestion 
Smum - He would never agree to mediation as it's 'a soft, poncey thing like counselling' in his opinion plus it would be difficult for me to be even in the same room as him. Currently I communicate with him via letter. I only phone him in an emergency, e.g. ds2 was in hospital last week so phoned him in that circumstance but other than that I have tried to do everything in writing as he has been unable to stick to whats been asked, e.g. when I requested email only unless it needed a quicker reply he would still phone and if I ignored him and texted him asking what was wrong he'd get aggressive saying I was being out of order not speaking to him. He also used to struggle keeping to texts only although has improved recently.
I'm not entirely convinced that they're not at risk though which is another big issue for me and one of the mai reasons I want to have contact altered. He and his mates smoke heavily while the boys are there, his flat is one room with only one window which I have asked hom to get a child lock on (2nd floor) and I've driven past (not spying but it's on the way home from the kebab house!) ad seen it wide open. I have stressed to the boys how vitally important it is that they stay away from the window no matter what. Because of this the boys have no escape from the smoke even when asleep, and I doubt if it's legal substances. ds2 has come back with severe, untreated burns which needed antibiotics once I took him to hospital. This resulted in a SS referral. They took none of my concerns seriously and said there was no problem. He is also up in court next week for possessio of cannabis & amphetamines. From what the boys said I think th initial charge was intent to supply but he got away with that. Solicitors are worse than useless. We are currently saving so that we can afford a better one than all the ones we have seen.
Riakin ??? 
Saggy snap! Do we have the same ex? 48 hours of xbox etc, 48 hours of coke (6-8 litres a weekend according o ds1 and no other drinks), crap food, chocolate chip cookies for breakfast, no lunch just sweets throughout the day and then food I don't allow for dinner. I don't allow for good reason, it'sd no good for ds2, ex is aware of it as he has complained to me that he can't handle ds2s behaviour. I wrote to him with suggestions that he asked for, incl a list of foods ds2 can't have and suggestions for things that are ok for him but he seems to have got the lists the wrong way round 
. They stay up until really late watching films in bed and suffer for it for the next couple of days. I mean, coke, sweets, x-box & late nights on tap, how do you compete with that?
Latemates - the small amount of contact is his choice. I have offered on many occasion for him to have them after school. I have sent emails telling him that if he wants to collect them after school and take them back for dinner at his to let me know. Every holiday I ask if he would like them fir longer. He has never taken me up on either offer. He has only been regular with his contact since DH moved in. Before that he would regularly let them down. At one stage he would let them down so regulrly that they only saw him about 3 times in 4 months. Guess what. They were different children, happy, healthy, well behaved, well adjusted withiut the upheaval.
I just don't know what to do for the best, it seems so unfair on them the massive change between the 2 homes but of course they love their dad and want to see him and so would be unfair to stop that, but I worry about their health, their minds, their safety while at his but don't want the resentment and upset from them if contact is stopped. 
Sorry this is so long, thank you if you've managed to get through it all.