REFILE-North Sea Crude-Gunvor buys two cargoes, Trafigura still bidding

(Corrects to make clear Gunvor bought Forties and WTI cargoes, not two WTI cargoes) LONDON, June 24 (Reuters) - U.S. WTI Midland and North Sea crude differentials rose on Monday on continued demand from Gunvor and Trafigura, with Gunvor buying two cargoes after Trafigura on Friday had taken four. * Keen buying interest across grades from the two trading firms supported the market last week. * The further gains on Monday came as a surprise to one trade source, who had expected differentials to drop this week. PLATTS WINDOW * Indications are on a free-on-board (FOB) basis unless marked as cost, insurance and freight (CIF) or delivered at place (DAP). * WTI Midland: Gunvor bought July 15-19 from Glencore CIF Rotterdam at dated Brent plus $2.50, or dated plus $1.25 on an FOB basis according to Reuters calculations, up from Friday. * Forties: Gunvor bought CIF Rotterdam July 6-10 from Total at dated plus $2.85, or about dated plus $1.47 on an FOB basis according to Reuters calculations, up from Friday. * Forties: Trafigura bid for July 4-25 at dated Brent plus $1.55. * Oseberg: Trafigura bid July 10-24 at dated Brent plus $3.05, up from Friday's bid. * Ekofisk: Trafigura bid July 8-25 at dated Brent plus $2.70, up from Friday's bid. * The day's trading leaves WTI as just the cheapest grade in the basket that sets the dated Brent price. (Reporting by Alex Lawler, Editing by Susan Fenton)