@QueenoftheAir
You have quoted guidance, not law. The relevant legislation can be found here: www.legislation.gov.uk/uksi/2020/1374/contents
Schedule 3A contains the tier 4 restrictions.
Exceptions: leaving home
2.—(1) These are the exceptions referred to in paragraph 1.
Exception 1: leaving home necessary for certain purposes
(2) Exception 1 is that it is reasonably necessary for the person concerned (“P”) to leave or be outside the place where P is living (“P’s home”)—
(a)to buy goods or obtain services from any business or service listed in [F3paragraph 17], ...
(c)to take exercise outside—
(i)alone,
(ii)with—
(aa)one or more members of their household, their linked household, or
(bb)where exercise is being taken as part of providing informal childcare for a child aged 13 or under, one or more members of their linked childcare household, or
(iii)in a public outdoor place, with one other person who is not a member of their household, their linked household or their linked childcare household,
By law, you are allowed to meet with one friend for exercise and there is no restriction on the distance you are allowed to travel.