I've been "out of the loop" for 10 years, now - so I don't know what local procedures might have been adopted. There may have been a "one off" occurrence which required vectoring to position a/c onto the ILS from the south. Certainly, Wycombe is correct to mention the need to avoid overflying Sark below 2000', but Guernsey Approach can usually position a/c onto the 27 ILS & still keep a/c over Sark above that height. I am presuming that we are talking about 27. Jersey would not want Guernsey going too far south of the 27 LOC on a frequent & regular basis (because that would infringe Jersey's airspace & vectoring). So, I am at a loss to explain why
you should have observed what you did.