In that case you'll be fine, they will be much better quality than most speakers attatched to any keyboard you will buy for £150.
I'd like to stress again that I would seriously recommend a second hand Yamaha CS1x synth, it doesn't just have synth noises it has a fullset of normal instrument and several drum kits. Oh and proper midi ports and knobs to twiddle.
One went for £75 a few days ago and one for £69 a few days before that.
That my friend is an absolute steal and will blow most keyboards out of the water, fantastic piano sounds some nice analogue style aphex twinish pads and a great Floydy preset called wish"U"here
Dammit, you may just end up bidding against me