Why do you think it will have changed?
All packages regardless of which one you are on can only deliver the maximum that your line can support.
If you were only getting 43Mbps on your previous package, which was not reaching the top speed of that package which is 55Mbps so it would not improve by changing package.
Can you run this checker and post back a screen shot of the results. Make sure you delete your phone number before posting.
If you have a Homehub 5 can you post the stats from 1-12 by logging onto the Homehub management pages then troubleshooting > helpdesk. http://bthomehub.home/
If you have the Smart Hub, (Homehub 6) can you go to hub manager then advanced then technical log and post the stats. http://bthomehub.home/
Is there any noise on your phone line? Dial 17070 and select option 2, there should be no noise between the announcements.
Moving you fibre plus gives you additional benefits but not faster speed
post stats from your hub. If hh6 then advanced settings then technical log information
if hh5 then troubleshooting then helpdesk
Going by the checker you should be getting more and you should have been more or less maxing out your previous package.
It may be that you have an underlying fault.
When you check your hub stats try connecting to the master socket/ test socket to see if the speeds increase. If they don't it could indicate that there is a line fault before the test socket on BT's side.
When you use the test socket make sure that any telephone extensions you have are "dead". There should be no dial tone at any of your phone extensions. If they have a dial tone it means you have star wiring and that is not good for Infinity and will need to be fixed.
here are the stats from the hub
Zsiunds like wiring really does need sorted and hopefully when wiring corrected you speed will improve and into estimated range
ive now got the wireing sorted stright into master socket nothing has really changed
Data rate:11.999 Mbps / 43.999 Mbps
Maximum data rate:17.581 Mbps / 55.725 Mbps
Noise margin:9.8 / 9.3
Line attenuation:23.3 / 17.0
Signal attenuation:23.0 / 17.0
i know there can be other contributing factors to max data rate but was expecting to get higher speeds. im roughly about 300m away from the cabinet can see it from the bedroom window.
i know the cable might go elsewhere but just did a quick measure follwing to bt cable ducts the best i could..
at my old house i was probably just under a km and that syncs about 39mbs.
does the max data get locked at different line profiles