So do we have anything to deal with it if it were hostile?
What can we use to shadow it??
I assume by we you mean UK, and although much diminished the UK still has submarines and surface assets that are capable of responding to both of your questions. True not as robust as before with the loss of MPA, smaller fleet and diminished dedicated maritime attack aircraft.
Shadowing is doable with a variety of surface and sub-surface assets. This deployment will also be tracked very closely by other nations, so I am sure their location will be quite well known, and help could be requested...