Seconded to a job then original job given away once I announced pregnancy: ask the expert

I have been employed by my current employer for approximately 3 years, but was seconded last year to another position as a project manager for 18 months due to end in January 2015. After external recruitment my post was covered by someone (A) on a fixed term condition due to end in January 2015. The terms of the secondment stated that ‘due to the length of the position length of the secondment it may not be possible for you to return to your substantive or any specifically nominated post. In these circumstances, you will be accommodated into a post at the same level/pay band as your substantive position’. On my return from Christmas leave, I was told that my role would change due to the director I was reporting to leaving. I assumed that as I was on secondment this would continue as someone was already in post covering my substantive role. My line manager changed and went back to my original manager (T). In March I announced to my line manager (T) that I was pregnant and due in September. Two weeks later in a weekly team catch up, he announced that due to the timescales there would be some recruitment in the team and my original post would be recruited to as they had decided to fill permanently. T stated that this would be advertised internally, and stated he hoped that A would apply for this position. I was very shocked to have this announced in the team meeting with no prior knowledge or consultation. After about a week I spoke to the HR director about this, and he told me not to worry, T could not do this and he would deal with it. The next day I received a letter from T stating that on the return of my maternity leave I would return to his team and ‘In these circumstances, you will be accommodated into a post at the same level/pay band as your substantive position dependent of staffing levels at the relevant time’. The HR director asked me a couple of weeks later whether this had all been resolved and I stated I have only been told I will have a job, but not what it is and I stated I was not happy as I did not want to be given just any job on the return from Maternity leave. This led to an HR advisor contacting me and telling me that everything has been done properly and not to worry. After my meeting with HR I found out that the post had been advertised internally for a week, and as no expressions of interest had been received A was to be made substantive. Even though normal policy is to recruit externally for substantive positions. In parallel to this in April due to office moves I moved from my permanent desk to a desk with the rest of T’s team. A hot desk policy was announced for the whole team. The policy states that ‘core team’ is expected to be in the office more that 50% of their time and will therefore be assigned a desk. Project staff are expected to spend more than 50% of their time engaged in project work and should therefore work outside the office. I currently do not have a defined role / job description, but I asked whether I would have an assigned desk as I have an office-based role. I was told that I am not included as part of the core team. This has meant that I can no longer use my docking station for my laptop, meaning I am using laptop all day every day. I completed a risk assessment my line manager asked me to complete two weeks ago raising the risk of not having a proper desk and docking station, but have not received a reply from him. Can you advise me whether my treatment has been acceptable?