Change Indicator Bulbs For Led?

[Tx2]

Just changed the number plate lights for a bright white LED; would like to change the orange indicator bulbs next, but although I have the correct fitting of LED bulb, they either flash really fast (telling me there is a faulty bulb?) or in the case of the front ones, not at all! Any ideas?

I was going to get some Philips Silver Vision (or whatever they were called) but they are discontinued and I can't find any replacements.

The LED's I fitted were 7440 type, description on invoice is : 15 LED BULB T20-3156/7440 W21W WEDGE

Like I say, they fit, but the rear just flash very fast, and the fronts not at all.

Hating the orange bulbs in there.... looks like a couple of eggs!