The Isles of Scilly are situated 28 miles to the west of Lands End. To get there you can take a light plane, or a ferry. There are places to stay on all the inhabited islands (St. Mary's, St. Agnes, St. Martin's, Tresco & Bryher), ranging from campsites to award-winning hotels. The islands are tranquil and beautiful. There are boat trips from the islands (weather permitting), so you shouldn't have a problem getting to Tresco once you're there.
A fair amount of walking is required and the paths vary from concreted "roads" to narrow paths on the moors, with the option of a small amount of scrambling over rocks. Some of the paths have short steep sections. The island is small though, so you don't have to cover a great distance. The climate is mild, but the weather can change abruptly, so have some wet weather gear with you.
There are toilets at the New Grimsby Quay, the Estate Office, and the Abbey Gardens. The New Inn, the Abbey Gardens and The Ruin Beach Cafe all serve refreshments. The island shop, Tresco Stores, is near the Estate Office and sells a good selection of food and a lot more. The Abbey Gardens are stunning and well worth a visit, there is an admission charge - it is not necessary to go into the gardens to complete the cache.
The trail is best started from New Grimsby Quay (N49 57.379', W006 20.497'), where most of the boats bringing day trips from the other islands land, depending on the tides. You can usually pick up a free map of the island from the information post along the road from the quay.
The location of the cache is N49 5A.BCD' W006 E.FGH', you need to find the numbers to substitute for the letters. The cache is a medium-sized rectangular plastic box. The gorse has grown up since it was hidden, so I wouldn't recommend attempting it in shorts.
1. N49 57.817' W006 20.907'
There are two obvious routes to this place. If you're happy scrambling over a few rocks on the path, and can manage a steep climb, the coastal route from New Grimsby Quay has great views. If you prefer a better path, turn up the path part way along the quay road, before Gallery Tresco, and go over Beacon Hill.
Building started here in the year abcd where C = c, D = d.
2. N49 57.475' W006 20.088'
Go inside, the door is usually unlocked, and there's a lovely painting to look at.
Sophia Frances died on December e fghi, where E = e-1, G = f+i.
3. N49 57.512' W006 19.656'
How many steps take you up to the archway? A = number of steps.
4. N49 56.872' W006 20.166'
Augustus was Lord Proprietor of the islands for jk years, where F = j and H = k-j.
How long did the "Commander" live? mn years, where B = n.