For new lifters, I suggest British Parts Northwest, here in Oregon. Their prices are very reasonable. If you buy them from DW or AH Spares then you will be paying full retail plus air freight from England. It all comes from the same source. If you want better oiling to your cam lobes, simply grind a small flat onto the side of the tappets. This is what DW does and then charges you a hefty fee for these "competition tappets".
I suggest MGC bucket lifters. They are about 1/3rd the price of the Healey pedestal lifters and have a small hole that allows oil to drain out and onto the cam lobes. Smith Brothers Pushrods in Bend, Oregon can make you up a set of tubular pushrods at a very reasonable price and they already know the size of the tips for the MGC lifters (it's different than the Healey lifters). New pushrods and MGC lifters will cost you less than a set of pedestal lifters. British Parts Northwest also has the MGC bucket lifters. This is what the real racers use.
I have to agree with this; from a stability/longevity standpoint, you're placing the pivot point of the pushrod
fractions of an inch (probably less than 1/4") above the lobe, instead of over two inches (>2") above it. Wear on the side of the lifters and the bores themselves is reduced, as is the operating friction and heat.
The MGB engine switched from pedestal to bucket lifter design at the 18V engine designation (GA/GB/GF, etc, engines with pedestal types) and thereafter all the MGB engines I built__maybe seventy-five (75?) of them__I would use the bucket lifters in. It's also a substantial reduction in valve train reciprocating mass.
There's nothing but an upside to the swap, and being able to get MGC lifters makes it doable; I'd follow Richard's recommendation for the pushrods.