Alison Lowe, Exclusive Castle Rentals, Nottingham, England
40 properties (from $8,000 per day).
Overall portfolio: $$$$
Lowe represents only fully staffed castles and manor houses, ranging from cozy (and intimate to truly grand. She'll send you details on properties after figuring (out exactly what you're after, and can arrange every aspect of your vacation, from a local guide to special services such as a Harry Potter-themed tour by car or (helicopter. A night in a spectacular castle may cost a king's ransom, but at least there's no minimum stay (44-115-975-6979; castles@adelanta.co.uk; exclusivecastlerentals.com).

London
Ann Christ, Farnum & Christ, (Bristol, Tennessee 22 properties (low season, $1,300-$3,500; high season, $1,300-$3,500). Overall portfolio: $
Christ has been renting London flats for more than 20 years and understands the importance of location in this sprawling city: All of her listings are in the most (desirable central neighborhoods. She steers clear of fussy accommodations with sky-high thread-count sheets in favor of those with low-key charm and comfort. (In addition to arranging for theater and concert tickets, she can get you a private tour of Parliament using her connections (800-366-2048; info@farnum-christ.com; farnum-christ.com).

GREECE
Anna Deimezi and Dimitris Giannakopolous, (White Key Villas, Athens
60 properties (low season, $5,070-$50,700; high season, $8,870-$63,360).
Overall portfolio: $$$
These two Greek natives have sourced high-end properties that span the mainland and the islands, many concentrated on the Peloponnese peninsula and in (the Cyclades. A lot of their homes are beachfront, the rest are no more than (a ten-minute drive away from one, and (all have sea views and come with daily housekeeping. Although a concierge (is always available, you might want to bring a guidebook, since Deimezi and (Giannakopolous don't leave house books with local info in their villas (30-210-721-05530; info@whitekeyvillas.com; (whitekeyvillas.com).

Ileana von Hirsch, (Five Star Greece, London
50 properties (low season, $10,000-$50,000; high season, $12,000-$50,000+).
Overall portfolio: $$$$
Von Hirsch hails from one of Greece's oldest shipping families, and thanks to her social connections, she has exclusive access to some of the country's finest properties—from historic village homes to sprawling beachfront estates. Don't try to view them on her Web site, though: Each property has its own password-protected Web page. After Von Hirsch speaks with you, she'll handpick up to ten suitable villas and send you the links. We love how conscientiously she discloses drawbacks and suggests alternatives: She'll advise which islands are best for avoiding the August meltemi winds, and where non-party (animals can find refuge from the sometimes pervasive noisy nightlife (44-20-8422-4885; ileana@fivestargreece.com; fivestargreece.com).