As you now know why, you should never, ever, EVER use the housebuilder's recommended/suggested solicitors. It will; never be in the buyers best interests and as you found out, often only benefits dodgy large housebuilders. You could and perhaps should make a complaint to the legal ombudsman suggestion 1) Collusion with the housebuilder (vendor) and 2) Professional negligence.
Regarding what Bloor Homes told you, showed you. It is inconceivable that any new homes slaes advisor would say
"they were not at liberty to divulge any plans or drawings..."The reality is they have a strict legal duty to do just the opposite under the
Consumer Protection for Unfair Trading Regulations 2008. Now however the onus is on you to prove what you were told and not told at the time of sale, which unless you recorded the conversations will be difficult. You could claim using the
Consumer Code for Home Builders Adjudication Scheme - created by and administered by the industry. You may be out of time to do so now.
Regarding the plans, anyone is entitled to amend the plans as they see fit. But there is a requirement to keep buyers informed of any material changes likely to affect their decision to buy/proceed. Regarding planning, most often any minor changes are rubber-stamped by the planning authority without so much as a cursory glance. However, it may be worth writing to them to point out a possible breach and let the council fight your corner. The more buyers/residents you can get to sign a letter or petition, the more likely the council are to sit up and take notice.