I have chased this up for you today and my colleague was indeed correct, there sadly is nothing we can do regarding this matter. They have advised an alternative would be to use WiFi or send on a different email account.
I am sorry it's not the answer you wanted as well but it is the correct one.
I requested one of our senior team look into this further for us and tehy have advised that ir may be that your home IP address is registered here https://www.spamhaus.org/lookup/
We aren't able to remove you from there but details on how this can be done are included on their site. Can you take the necessary steps to get this your IP address removed and see if this resolves the issue.
Please remind me, who is ultimately responsible for and has control over the provision of residential IP addresses?
Who actually "owns" an IP address, the end user (customer) or the provider (ISP)?
The answer, of course, is the ISP (well sort of), but the issue here is the very real distinction between what a company could theoretically do as opposed to what they are prepared to do because of company policy. As an example, we sometimes see requests from users to change their public IP address (and not always for particularly good reasons), the usual response is to say that VM can't do that. Well technically that's a nonsense, whoever controls the infrastructure (in this case the DHCP servers) can do whatever they like - what probably is the case is that VM have no administrative structure or mechanism in place to do this. Effectively then it amounts to the same thing, any anyone who has ever had dealing with a large, bureaucratic company will know of how difficult it can be to get changes made.
@TheBoyGreen as has been mentioned above, when you try to send an email via your VM account, the servers (and this is somewhat oversimplified), first check to see if the address that your device is connecting from is listed on one or more 3rd party list. From what you have described, it would appear that both the address of your home broadband connection and the address your phone receives when connected to the local 4G tower are included on it. Now your home IP address is yours and your alone so you could take action to get it delisted - this is the advice posted previously about a device on your network becoming infected with malware and sending out spam. If you can track that down and deal with it, at least this address should be delisted.
The 4G connection is another story, you share this address with many other people using the same tower, if any of them have a compromised device then that address gets listed and you are guilty by association, so to speak.
These 'blacklists' are maintained by a third party and neither VM nor 3 can 'demand' that the address be removed, now there is a sort of justification for VM referring to this list when connections are made from your home broadband (although I am starting to come round to the idea that it's probably causing more problems than it is supposed to solve), I can see absolutely no good reason for doing the same with what are called CGNAT'ed addresses ie the 3 4G connection, it's not as if VM nor you, nor 3 can do anything about the listing - VM could chose not to block based on inclusion in specific circumstances but choose not to for what they perceive as security reasons!
Bottom line is that a member of the VM email security team could probably resolve this with a small edit to an access control list, your problem is fixed although the engineer would probably be looking for a new job the next day for blatantly violating company security policies. Other than passing on the recommendations to management, there's nothing the forum team nor email team can practically do to help you - will it be enough to get them to change policy? Probably not!
Not particularly helpful post I'm afraid, other than trying to throw a bit more light onto the situation, you do appear to be unfortunate in having been listed twice. All I could suggest is that you firstly try to find the compromised device on your home network and deal with it permanently, that will get your home address delisted within a day or so, and secondly investigate alternative email providers (Outlook, gmail etc) with a view of gradually migrating across to them - always useful if you ever decide to leave VM as at least you won't lose your email address as well.