Plusnet, snooping?

[#1]

Like many of you I have a web mail address.
The other day after reading my Google mail, I started looking at some of the features on my page.
At the bottom of the page I came across this one where it gives my PCs IP address.
To my horror it also gave a list of two other IP addresses that had also logged into my account.
(IP 87 155 109 114)  (IP 87 155 17 201)
I did a trace on these two addresses, only to find they had originated from Plusnet technologies.
So the question I have to ask, is my internet provider logging into my account to read my mail.
Or is there some other benign explanation for these IP addresses to be there.

[#2]

If you are on a dynamic IP address these could well be your old addresses.

[#3]

You are assigned a dynamic IP when you connect and those two addresses have recently been leased to you.

[#4]

Thanks for the explanation.
I have just done some research into Dynamic IP addresses ,so I can see how this might occur.
It might be a good idea if Google mail were to point this out as well, rather than just to say that other computers have logged into the account.
Many thanks