I am in a similar situation. I was granted 10 year route in 2013 on my application which i made in 2011. At time of extension my solicitor changed it to 5 year route in 2015.
Now I have applied for ILR after completing 5 years , 2.5 on 10 year route and 2.5 on 5 year route on the basis that my original application was before july 2012 law change ao i should be considred for ILR. Been over 7 months no response from home office.
My solicitor said worst case scenario would be that they will put me back on 5 year route as an extension of previous leave to remain. The decesion can also be challenged in court. So its a 50 50 chance and wrth taking.
So my advise would be to consult your solicitor and go for it
Have u done B1 and Life in the uk?