Thats the one in the pharmacy.....so 50 quid doesn't seem too extortionate then.
I have something like that one. Curiously, it's still in its box as I bought it a couple of years ago when the battery on my current one (which is just a previous model of that) dropped from 5 days after charging to 3 days. I've been waiting for it to die ever since but it still keeps on going at 3 days after charging. I must have had the original one for about 7 years now.
The prices of these things seem to go up and down all the time but it's noticeable that there are random deals on in places like Boots or the supermarkets particularly around Christmas time. Usually it's better to buy the plain Jane packs rather than the ones with spare brushes or toothpaste included. The brushes are cheap enough in multipacks and most people choose their own toothpaste anyway.
I used to think that electric toothbrushes were just a gimmick after decades of manual brushing but it has been a revelation. One of the few modern appliances that I've ever thought "I shoulda got one sooner". Brush heads are available everywhere, even supermarket own brands. I initially used to get a multipack from Amazon but found over time that quality became variable, particularly for some of the ultra cheap packs which notably didn't last as long as slightly more expensive ones.