Hi - stipulation in the NICE guidelines is for weekly CONTACT not weekly visits, when pregnant and diabetic. I was going to the hospital around once every four weeks in the beginning, up to once every two weeks by the end. I would phone in my blood sugar results each week and get advice over the phone. Only if there was a problem that couldn't be resolved over the phone would I go in in addition to these times. YOu are legally entitled to paid time off for antenatal care so don't worry about that.
Towards the end i found it hard to work, due to frequent daily hypos, so I stopped at 31 weeks, although if I'd had to stay a bit longer I probably could have (my boss adapted my role so that I wasn't partaking in meetings during hypo danger times towards the end). I took annual leave for five weeks then started my maternity leave at week 36 - induced at 38 weeks.
If it is not safe for you to do your job whilst pregnant without it endangering your health, your employer will be obliged to adapt your role, or if unable to do so suspend you on full pay, whilst you are pregnant (I work in HR btw!). These are legal rights.
I found that my employer was very sympathetic to me, despite my frequent hypos, no one ever said anything (except one girl in payroll who made a sarky comment when I went down to half days towards the end, I told her where to go). I think they were just concerned for my welfare esp when I collapsed one day with a blood sugar of 2.3, but although my boss suggested I take early mat leave at that point, it was never forced upon me. I also found educating my immediate colleagues in what a hypo was, how to treat it etc was useful.