I live in Scotland and have been banned twice in 3 years. My current ban was for 36 months reduced to 27 with the DD Awareness Course.
I have also joined AA and find it therapeutic passing on my experience on this forum.
This probably won't help you much, but I've said it before and I'll say it again, sentences in England are much tougher than in Scotland.
I had a reading of 124 for my first offence (limit is 22) so was 6 times the limit, but only received a £400 fine and a 2 year ban. No Community Service. I ended up going to court after 3 nights in police custody, unshaven, holding up my trousers with one hand as they would not allow me a belt. I'm not sure just how much your actual appearance/demeanour matters to the judge/magistrate.
A couple of months after I received my licence back I began drinking again and was caught with a reading of 96, over 4 times the limit. This time I received a 36 month ban reduced to 27 with the Course and another £400 fine. Again no prison or Community Service.
I was also lucky enough that neither of these were picked up by the local newspaper. Thankfully I didn't crash and no one was injured.
Travel to Canada is out for 10 years from the date of your last conviction.
The USA would not be an issue, but there is a question on the ESTA that asks the following;
Now I don't know whether a bollard and damage to your own car would constitute serious damage, but you never know. There don't appear to be any questions regarding ANY criminal convictions and I have heard of other people on this forum going to the USA using the ESTA form.
Mexico I believe, is also off limits forever with a DUI conviction, but again, they have no way of checking this without input from yourself as they do not have access to the databases that record your conviction (neither do the USA or Canada, although someone may know different.)
Regarding Home Insurance and Contents cover, I am with Nationwide for both and once I became aware that this could be an issue, I contacted them and asked the question and was pleasantly surprised to discover that they would still provide me with insurance cover. In saying that my premium for this year has just gone up by about £50 including many years No Claims Discount, so perhaps something is going on.
I was insured by Admiral, and my NCB which I asked for says it is valid for 3 years, which will hopefully give me time to insure any new car I buy (although not with Admiral I imagine.)
So good luck on the day.