caldera,
What do you mean "absolute ceiling"? That it was going too fast is obvious, but I think you don't understand what the RAF meant by an aircraft's ceiling. All that meant was the altitude at which an aircraft's climb rate dropped below 500ft/min. You could go higher, but operationally it wasn't really useful.
The page Gyrene81 quotes above has this passage:
Performance: (Early B.Mk I) Maximum speed 275 mph (443 km/h) at 15,000 ft (4572 m). (Late B.Mk I) Maximum speed 287 mph (462 km/h) at 11,500 ft (3505 m), 275 mph (443 km/h) at 15,000 ft (4572 m), 260 mph (419 km/h) at 19,400 ft (5913 m); cruising speed 234 mph (377 km/h) at 21,000 ft (6401 m), 200 mph (322 km/h) at 15,000 ft (4572 m); stalling speed (clean) 95 mph (153 km/h) at 60,000 lbs (27211 kg);
normal service ceiling 23,000 ft, nominal service ceiling 24,500 ft (7468 m);
absolute service ceiling 24,671 ft (7500 m); climb to 20,000 ft (6096 m) in 41 minutes and 40 seconds; initial rate of climb 250 ft (76 m) per minute with full bombload. In a hard dive the prototype aircraft achieved speeds reaching almost 400 mph (644 km/h) with production aircraft (operational loadout) being limited to 360 mph (578 km/h).
Another interesting note in this paragraph is that the plane could
almost reach 400mph in a hard dive (with the prototype - production aircraft, only 360mph), whereas in AH, I have film of one doing 484mph up high.
Absolute ceiling:
http://www.thefreedictionary.com/absolute+ceilingThe highest altitude at which an aircraft can maintain level flight.
Engine power for the various Lanc variants (from same source):
Powerplant: (B.Mk I) Initially four Rolls-Royce Merlin XX or 22 Vee 12-cylinder liquid-cooled inline engines each rated at 1,280 hp (955 kW) for take-off and 1,240 hp (925 kW) at 2,850 rpm at 10,000 ft (3050 m) with a maximum power rating of 1,480 hp (1104 kW) at 3,000 rpm at 6,000 ft (1830 m). Late production B.Mk I aircraft being equipped with four Rolls-Royce Merlin 24 Vee 12-cylinder liquid-cooled inline engines rated at 1,620 hp (1209 kW) for take-off and 1,240 hp (925 kW) at 2,850 rpm at 10,000 ft (3050 m) with a maximum power rating of 1,640 hp (1223 kW) at 3,000 rpm at 2,000 ft (610 m). (B.Mk II) Four Bristol Hercules VI 14-cylinder two-row air-cooled radial engines rated at 1,615 hp (1205 kW) for take-off and 1,675 hp (1250 kW) at 2,900 rpm at 4,500 ft (1370 m) with a maximum power rating of 1,675 hp (1250 kW) at 2,900 rpm at 4,500 ft (1450 m). The radial engined Lancasters had a higher top speed but also had a higher fuel consumption. (B.Mk III) Four American-built Packard Merlin 28 Vee 12-cylinder liquid-cooled inline engines each rated at 1,300 hp (970 kW) for take-off, or four American-built Packard Merlin 38 (Merlin 22) Vee 12-cylinder liquid-cooled inline engines each rated at 1,390 hp (1037 kW) for take-off. Some later B.Mk III aircraft had the American-built Packard Merlin 224 (Merlin 24) Vee 12-cylinder liquid-cooled inline engines each rated at 1,620 hp (1209 kW) for take-off. All Merlin engines used a mechanically driven, two-speed, single stage, centrifugal supercharger. Note: Rolls-Royce engine marks up to XX (twenty) are distinguished by Roman numbers, while marks above that were distinguished by Arabic numericals.
thats how the RAF did fighters, not sure if they used the same for bombers (500fpm is pretty good for an EW buff) 
edit: quick offline test from 30k base:
~51,000lb, 3x2k bombs (they look like 2ks in the film, might be 1ks), ~25%
@30k 542fpm
~71,000lb, 14x1k bombs, ~100%
@24k maintains level flight
mass makes a big difference ...
If the service ceiling(100ft/min climb) is more or less 23,000ft, it shouldn't be climbing five times that rate at 30,000ft with eggs aboard.
