The bottom image is a circuit I'm trying to make. However, I have loads of 2n3055s so wish to change the power transistor. Im aware that it can be done as its just a single transistor and that all other polarities need to be changed.
Im hoping that my modifed cct is now correct and so would really appreciate someone much brighter than me checking it pls.
Many thanks in advance

 

It is not going to work. The transistor is pointing the wrong way.
Why did you turn all the voltages around?
That makes the circuit confusing. Go back to the original drawing and replace the transistor.

 

its just a single transistor and that all other polarities need to be changed.

Nope! Only the pulse (output from the 555) needs to be inverted, and remember that a PNP is to source and NPN is to sink. Google 'how to use transistor as a switch' and you'll see

 

You can use an NPN by connecting the emitter to ground with the collector to the load, and the load connected to V+.
That's called a low-side switch.
The main difference is that the transistor is now ON when the 555 output is high instead of low.

 

Just replace the transistor and drive the LEDs low side instead of high side.

Why did you redraw a schematic that was mostly readable upside down? Better schematic symbols have the inputs primarily on the left and outputs on the right to facilitate the preferred left-to-right and top-to-bottom flow.

 

I think if you invert the output section you will also need to invert the LDR section as well.

 

I think if you invert the output section you will also need to invert the LDR section as well.

Yes, he would.

 

If you want to use a Npn , just reverse the sensor input and pull the LEDs down to ground, like this...

 

If you want to use a Npn , just reverse the sensor input and pull the LEDs down to ground, like this...

View attachment 204803

Thank you DD. MUCH appreciated.