I have had a look at our renewal contract Ellie. BT are calling it Halo 2. We were due for renewal and I must confess reluctant to change internet providers in these strange times in case we had bother that meant we could no do the online watsit stuff. So we "had a word" with the BT accounts line staffers and pleaded old age decrepancy, poverty, and general ignorance to obtain a "deal" from them. You say that you are on a 0.5 mg Broadband set up. Sorry but I cannot work that out. I have just done a test on ours whilst we have at least 5 units hooked up to the router(including 2 sky plus units) and we are pulling 64Mbps( Megabits per second) download, 48 Mbps upload with a Ping( latency) test of 1 Ms. This is not bad considering our location and cannot be bettered here without a discrete fibre optic connection right into the house. You can check your Broadband speeds here at no cost and compare them with what you are supposed to be getting and what you are being offered.
https://www.bing.com/search?q=broadband+speed+test&cvid=3c18cd89d451430e9e8c9ba166010ab6&FORM=ANNTA1&PC=U531
P.S You techies....I was surprised, and pleased, with the latency test as it used to be woeful.