Here's a list of some of my favourites - they're not all great, but all have at least plenty of character and lots of good holes, at least enough to interest a GCA groupie: Aldeburgh (6323), Swinley Forest (6045), Sandiway (6435), Sandy Lodge (6328), West Cornwall (5884), St Enodoc (6243), The Berkshire (Red 6379, Blue 6260), The Addington (6242), Burnham Beeches (6449), Denham (6462), Gog Magog Old Course (6398), Royal Jersey (6100), Royal Guernsey (6215), Delamere Forest (6328), Perranporth (on Paul Turner's recommendation which is good enough for me) (6286), Seascale (6416), Cavendish (5833), Prestbury (6359), Yelverton (6351), Broadstone (6315), Ferndown (6452), Isle of Purbeck (6295), Parkstone (6250), Sherborne (5882), Brancepeth Castle (6400), Broadway (6228), Minchinhampton Old (6019), PAINSWICK (4780), Blackmoor (6213), Liphook (6167), Stoneham (6310), Canterbury (6249), Knole Park (on recommendation) (6266), North Foreland (6430), Royal Blackheath (6219), Walmer & Kingsdown (6444), Bolton Old Links (6469), Clitheroe (6326), Fleetwood (6308), Pleasington (6445), Charnwood Forest (9 holes 5960), Lincoln (6438), Seacroft (6479), Manchester (6450), Heswall (6492), Mill Hill (6309), Gt Yarmouth (6330), Royal West Norfolk (6427), Sheringham (6495), Bamburgh Castle (5621), Huntercombe (6173), Tadmarton Heath (5917), Luffenham Heath (6315), Bath (6442), Beau Desert (6310), Whittington Heath (6490), Felixstowe Ferry (6308), Ipswich (6435), Royal Worlington (9 holes 6210), Woodbridge (6299), Camberley Heath (6326), Coombe Hill (6293), Farnham (6313), Hankley Common (6438), New Zealand (6075), Royal Mid Surrey Outer (6385), Royal Wimbledon (6348), St George's Hill (6496), Tandridge (6250), West Hill (6368), West Surrey (6300), Woking (6340), Worplesdon (6440), Crowborough Beacon (6273), Piltdown (6070), Royal Ashdown Forest (6477), Rye (6308), West Sussex (6223), High Post (6305), Ogbourne Downs (6363), Blackwell (6230), Harrogate (6241), Hallamshire (6333), Lindrick (6486), Huddersfield (6432), Sand Moor (6429). Then there are Scotland, Wales and Ireland - someone else's turn.
Sunningdale Old is listed as 6581 so it's just too long nowadays.